To provide a rotary switch device, by which larger space for mounting is not required.

A size detector 200 includes a rotating shaft member 202, wherein a user operating portion 202a and a size display unit 202b with each size described are integrated. The rotating shaft member 202 rotates about a shaft 202c, penetrating its central portion. Four uneven pieces 203 of the same shape are fixed to the shaft 202c in line in the longitudinal direction of the shaft 202c. A 4-bit on-off pushbutton switch device 205 is arranged near the shaft 202c of the rotating shaft member 202. Four pushbutton switches 205a, 205b, 205c, 205d are fitted to the pushbutton switch device 205, and the four pushbutton switches 205a, 205b, 205c, 205d moves in the direction of an arrow mark (A) in proper timing, and these are turned on, when these move a predetermined distance in a direction away from the shaft 202c.