PURPOSE: To make a key board switch which is highly dust proof and highly moisture proof, come into being by detecting the values of resistance of both a plurality of No.1 pressure sensitive resistor members formed roughly in parallel with one other and a plurality of No.2 pressure sensitive resistor members formed roughly in parallel with one another in such a way as to be perpendicularly intersected with No.1 members.

CONSTITUTION: Pressure sensitive members 2 and pressure sensitive members 3 are formed in the directions each of which is intersected with each other while being concurrently formed into a matrix when viewed from the upper surface of a flexible sheet 1. Each end of the pressure sensitive members 2 and each end of the pressure sensitive members 3 are connected with detection circuits detecting each value of resistance of the respective members. The pressure sensitive members 2 and 3 are of nature that electric resistance is changed by external stresses. Switching is therefore actuated by means of change in resistance, a key board switch which is highly dust-proof and moisture-proof, can thereby come into being.