PURPOSE: To detect the presence/absence of recording paper in a paper feeding tray and measure the state of the recording paper with a simple and inexpensive constitution by accurately measuring the state (moisture content) of the recording paper.

CONSTITUTION: This form detecting device is provided with two conductive rollers 103a and 103b which are arranged at an interval L near a calling roller 102. In addition, a supporting member 103c which supports the rollers 103a and 103b and feeding paper carrying section (control means) which applies a voltage across the section of recording paper 201 having a length equal to the interval L from the rollers 103a and 103b and discriminates the moisture content of the paper 201 from the value of an electric current which flows when the voltage is applied.