To provide a hot water toilet seat with an automatic washer which can be set on toilet seats having different sizes.

There are provide with a stool, the hot water toilet seat with an automatic washer, a base, a seat part, and an upper lid. The base is equipped with an adjustable connection member connectable corresponding to a tapped hole formed in the stool at the bottom part. The connection member include a rail, a slide block, a screw, and a fixed pad. The rail is set on the bottom part of the base and includes a slide block slidable along the rail inside. A groove is set in the vertical direction against the rail on the slide block. The screw fixes and connects the fixed pad to the rod body. The bottom part of the screw is extended penetrating through the groove to bring the surface of the fixed pad and the bottom face of the slide block in contact with each other. A tooth shape pad like saw tooth is formed on the surface of the fixed pad. A groove corresponding to the tooth shape part is set on the bottom face of the slide block.