Mobile phones are in a trend of having thinner configuration due to emphasis on the design. Thus, in order to meet this demand, the present invention aims to thin the key sheet portion as much as possible. The present invention provides a thin key sheet 1 comprising a key top 2 made of a metal or a resin having on the front surface or the back surface indications such as letters, symbols, graphics or the like indicating the functions of keys, a key pad 3 made of a material having rubber elasticity such as a silicone rubber or various elastomers for supporting/fixing the key top, an EL element 8 formed on the back surface of the key top by means of printing, and a printed circuit board 5 on which a switch element is provided at its surface for turning ON/OFF of an electric circuit by the pressing of the key top 2 and on which a circuit pattern involved therewith is formed.