PURPOSE: To enable a person having difficulty in posturing a half sitting to use easily a lavatory pan by providing a plurality of elastic bodies having mutually different elastic forces to be used selectively in a driving source for lifting a stool seat body mounted on a Western style lavatory pan body with a stool seat lift device.

CONSTITUTION: A lift type stool seat is provided with a stool seat lifting device 3 for lifting a stool seat body 2 mounted on a Western style lavatory pan body. This lifting device 3 is composed of a drive support column 5 having a stool seat carrier 4 supporting the stool seat body 2, fixed to the lifting device and lifted by a gas spring 7 and a lift guide frame 9 or the like to guide the lift of the support column 5. When the stool seat body 2 is lifted up by the elastic force of the gas spring 7 and a load is applied to the stool seat body 2 by the seating of a person, the stool seat body 2 is lowered while the spring 7 is constracted to energize an upward elastic force, mitigate the weight of a one's body and aid a person in posturing a half sitting. Two gas springs having mutually different strength are used selectively.