PURPOSE: To provide a paper sheet cassette device capable of detecting the size of sheets accurately.

CONSTITUTION: A paper sheet cassette device is provided with a sheet cassette 11, a tail guide 12 arranged slidably in the feeding direction of sheets, guides 61 and 62 arranged slidably in vertical direction relative to the feeding direction of the sheets, a drum which is rotated interlockingly with the movement of the tail guide 12 and on which drive projections are formed, and a slider 72 which is reciprocated interlockingly with the movement of the guides 61 and 62 and on which recessed and protruded parts are formed. Also it is provided with multiple switches and a switch operating body 53 which are arranged oscillatably, engaged with the drive projections and recessed and protruded parts, and turns on and off the switches according to the engaged conditions. Thus a specified switch is turned on and off according to the rotational position of the drive projections, and also a specified switch is turned on and off according to the position of the recessed and protruded parts.