The man is accused of accepting bribes in a case linked to the Milan-based firm, Swe-Co Sistemi, a distributor of electrical goods.
On Thursday, Italy's financial police found some €267,000 in cash, divided into envelopes that were distinctly connected to their supplier, hidden in two security boxes.
More cash was found in the home and offices of the judge, bringing the total to €300,000.
Police believe the money was not earned from his legal activities, but through bribes, especially after his secretary claimed he worked on “few cases”, Corriere reported.
Police caught wind of the hidden cash through wiretaps and a witness statement from the secretary.
A female colleague of the judge was also arrested on Thursday on suspicion of corruption.