To provide a key top structure having superior design, while eliminating the printing of direction index in an external case part, reducing the manufacturing cost, enabling visual and tactile index, and facilitating blind touch.

A directional function contact 13a formed into a pattern is arranged on a main board, and a direction key 22a integrally formed with a top surface of a key top 16 is made to pass through a key through-hole 24a formed in a panel assembly 14 facing opposite to the directional function contact 13a, and projected slightely from the top surface of the panel assembly 14. Triangle direction indexes (22a2-22a5) projected slightly from the top surface of the direction key 22a are arranged integrally on the top surface of the direction key 22a at four positions in the upper, lower, right and left directions corresponding to the directional function contact 13a so as to visually and tactilely show the direction.