Christopher Gorman, 54, had been keeping the animals in his back yard.
He was also found guilty of leaving the dogs in an unsuitable environment where they were living among excrement. Gorman was reported to the Scottish SPCA by concerned buyers.
Sentence at Airdrie Sheriff Court was deferred.
Sheriff Derek O’Carroll said Gorman had refused to accept responsibility “for any and every shortcoming in care for the dogs which he was responsible for”.
He said: “Many dogs, including puppies, had suffered unnecessarily some to a great extent and that was wrong and that was illegal.”
He said one dog had suffered so badly it had to be put down.
Sheriff O’Carroll described the offences as so serious that a jail sentence was a possibility.
The Crown said Gorman had assets of more than £1.2m.