In a key switch device, the depressing load applied to a key top 11 when depressed is defined by a function (equation 26) expressed by: a distance L between the rotation point o of a support shaft 30 of a first link member 12 at a first engagement portion 17 in the key top 11 and the slide starting point s of a support shaft 26 of the first link member 12 at a third engagement portion 40; a distance L1 between the rotation point o and the acting point m at which the urging force of the coil spring 15 acts on the first link member 12; an angle &thgr;4 between a line segment extending from the rotation point o to the slide starting point s and the direction along which the support shaft 26 of the first link member 12 at the third engagement portion 40 is allowed to slide; and various characteristic values of the coil spring 15. In relation to the depressing load curve P defined by the function, based on the difference in loads between the maximum point P1 in an upward projecting curve and the minimum point P2 from which the depressing load is increased after the switching operation, the key clicking function is performed.