The Conservative Member of Parliament visited Slenderella on Queen Street, had a walk around the factory and met with the workforce.
Gary Spendlove, manager of Slenderella said: "He was very interested in the company and the business, how we had grown and developed.
"He was very interested in the textile industry in the area, in the Brettles name and how plans for the museum were progressing."
Mr McLoughlin also saw how garments were designed and made up, saw fabric and current stock and chatted with various members of staff.
He said: "It was a fascinating visit. Here is a company that only started a few years ago, has found a niche in the market and is doing very nicely indeed.
"Last time I visited it was the old sock factory and it is nice to see the building being used for textile use again."
Later on in the day Mr McLoughlin held a community surgery which was open to all.
This provided an opportunity for people to bring up issues and concerns that they had regarding any aspect of council activities and policies.
Mr McLoughlin said: "It was a very busy surgery with issues ranging from road repairs to child tax credits and planning matters.
"People from all areas attended not just from Belper, we had people coming from Matlock and Ashbourne as well."
Later in the week Mr McLoughlin will visit Ashbourne, Derby, Wirksworth, Taddington and Winster