Treasury Secretary Steven Mnuchin said Wednesday the Justice Department is right to be looking into Amazon's practices as part of its antitrust review of big technology companies.

"I think if you look at Amazon, although there are certain benefits to it, they've destroyed the retail industry across the United States so there's no question they've limited competition," Mnuchin told CNBC's "Squawk Box."

"I think it's very good that the attorney general is going to look into this. I think it's an important issue and I look forward to him reporting back to the president and hearing his recommendations," said Mnuchin.

The Justice Department said Tuesday it is opening a broad antitrust review of big technology companies, sending shares of Amazon, Alphabet and Facebook lower in off-hours trading. The DOJ said it is looking into how major online platforms have "achieved market power" and how their practices may have "reduced competition, stifled innovation, or otherwise harmed consumers."