PURPOSE: To obtain the subject safe and harmless detergent effective in preventing the deposition of fat on the wall of a pipe by using an enzyme lipase as a principal agent and adding sodium bicarbonate as a swelling agent and an N-acylamino acid as an enzymatic activity preserving agent.

CONSTITUTION: The objective detergent having a pH of 7-9 (in the form of aqueous solution) can be produced by using (A) an enzyme lipase having a fat-decomposition activity of 20-60U per 1g of fat (in terms of lard) and adding (B) sodium bicarbonate as a swelling agent and (C) an N-acylamino acid as an enzymatic activity preserving agent. As necessary, the detergent may be incorporated further with a frothing agent such as tartaric acid, a pH-modifier such as sodium carbonate and protease and/or amylase.