A toilet seat device includes a main part, a toilet seat, a load sensor, a controller, and a memory. The toilet seat includes a seating part where a user is seated, and a support leg part supporting a load applied to the seating part. The load sensor is provided in the support leg part and detects the load applied to the support leg part. The controller performs at least a body weight measurement of the user based on a detection result of the load sensor. The controller includes a register mode and a normal-use mode in the body weight measurement. The register mode includes determining an estimated value for estimating the total body weight of the user from the seated load. The normal-use mode includes estimating a load value relating to the total body weight of the user based on the estimated value.