A motion member (1) urged by an application spring 4 is made to collide with a surface of a sheet material supported by a support member (14) so as to be deflectable and deformable. The velocity of the motion member (1) during the collision process is detected every second by a measuring portion (17) of a laser Doppler velocimeter. A control circuit (121) measures the velocity of the motion member (1) immediately before the collision of the motion member (1) with the sheet material, the time period of deflection deformation until the sheet material collides with an opposing member (15), and the time period of compression deformation after the collision of the sheet material with the opposing member (15), and outputs a result thereof as sheet material information to a control portion (120). The timing at which the sheet material collides with the opposing member (15) is detected by an output of a piezoelectric element (16) connected to the opposing member (15).