To provide a pressurizer for a seat of a hot water bidet easily and compactly installed onto the seat of the hot water bidet, and capable of pressurizing water for comfortable washing.

In a pressurizer to be installed on a toilet to supply water to an existing hot water bidet seat 10 after pressurizing water stored in a tank 36 by a pump 34, an infrared ray signal 20 generated by an infrared ray operator 11 installed as an attachment to the hot water bidet seat 10 to the hot water washing toilet seat 10 is monitored. A pressurization control means to determine an actuation condition of the hot water bidet seat 10 rotates or stops the pump 34 as a pressurizing means based on the signal 20 received.