The invention provides a pressure detecting device containing a pressurized member having a contact surface that is subjected to pressure due to contact with a pressurizing means; and a piezoelectric member that is arranged facing the pressurized member and that includes a polymeric piezoelectric material having a piezoelectric constant d14 of 1 pm/V or more as measured by a displacement method at 25° C., and a ratio IEb/IEa between a product IEb of a cross-sectional secondary moment Ib and a Young's modulus Eb of the pressurized member, and a product IEa of a cross-sectional secondary moment Ia and a Young's modulus Ea of the piezoelectric member, is in a range of from 102 to 1010.