Abstract: The slide support base 62 protrudes from the supporting wall 56 of the support recess 52 in the casing main body 14 and the tube-shaped support part 122 on the side of the toilet lid 100 is supported by and capable of sliding over its cylindrical surface 65a. The rotational pin 70 of the viscous resistance mechanism 80 protrudes from slide support base 62 and the rotational pin 70 fits in the fitting recess 132 on the side of the toilet lid 100. That is, the toilet lid 100 is pivotably supported to the casing main body 14 by two support structures. To remove the toilet lid 100 from the casing main body 14, the toilet lid is raised to the upright position and then applied with upward force to be pulled out. Since the opening 124 and the opening 136 are formed in the tube-shaped support part 122 and the fitting recess 132, the toilet lid 100 is removed from the casing main body through them.