However local councillors said they had received dozens of emails supporting the arrival of the discount brand in their community.
They rejected the advice of planners and gave the new store the go-ahead.
At a virtual meeting of the council’s planning committee, local ward members rejected the description of the site of the new store as “countryside”.
Councillor Pauline Winchester, who called in the application, said: “The fact planning has called it in the countryside is not quite true. It is exactly opposite Asda and Straiton is a couple of hundred yards away.
“With the advent of the high cost of fuel, the possibility of Edinburgh having a congestion charge, everything needs to be discussed by all of us.”
Councillor Winchester said she had received 15 emails supporting the new store and none against it.
Fellow ward councillor Peter Smaill added: “I think it is all about intensifying competition at Straiton. The land itself is not of any particular landscape value so on the balance of public advantage I think the case is for this to be approved.”
And councillor Kelly Parry, also representing the Loanhead ward, said: “I’ve had at least 21 email over the last few days as I am sure lots of members have.”
Planning adviser Peter Arnsdorf said regardless of how they felt it was classed as countryside in the local authority’s local development plan.
And he said town centre policies required officers to look at whether the new store could be better placed in the town centre itself or the nearest vacant sites.
Roslin and Bilston Community Council and Damhead Community Council both objected to the Aldi store, arguing it was on the wrong side of the A701 and should be on the same side as Straiton Retail Park, as well as raising concerns about access to the new store.
And Straiton Retail Park’s bosses objected saying there was no need for additional land to be given for retail.
Planning convenor Councillor Russell Imrie also voiced concern about allowing the store on the other side of the A701 from the retail park and creating a new retail corridor on greenbelt.
However Gorebridge councillor Ellen Scott told the committee she would be delighted if stores like Aldi were coming to her ward, issuing a plea to retailers to consider her ward in the future.
The committee unanimously agreed to approve planning permission for the new Aldi store.
An Aldi spokesperson said: “We are very pleased with the decision, and would especially like to thank the local residents who were so supportive of the application and our proposals to come to Straiton.
“Following the success of our recently opened store in Dalkeith, we can’t wait to bring our award-winning offer to Straiton, further enhancing our presence in Midlothian, whilst creating up to 35 new job opportunities and increasing the choice and value for shoppers in the area.”