John Hartshorne was spotted by the Health and Safety Executive inspector on January 23 as he carried out repairs on the roof of the Walmsley's Furniture Superstore.
He was undertaking the work with two employees.
Mr Hartshorne today pleaded guilty to a breach of the Work at Height Regulations at Barnsley Magistrates' Court.
HSE Inspector David Bradley said: "This particular project was very poorly planned, and there were no controls in place to prevent falls from the roof where in areas there was potential to fall 10m to the ground.
"Thankfully no-one was injured on this occasion but had we not been passing and taken action, the outcome could have been quite different, and even tragic."
Mr Hartshorne was also ordered to pay £500 costs.