A pedal device for adjusting pedal effort includes a housing fixed to a car body, a pedal arm that is hinged about the housing, an elastic member that is disposed between the housing and the pivot end of the pedal arm and provides a return force to the pedal arm, a pedal effort adjusting unit that is movably disposed in the housing and has a sloped portion for adjusting a pre-compression force to the elastic member, and a pre-compression force setting unit that sets a fixed position of the pedal effort adjusting unit with respect to the housing and keeps a pre-compression force applied to the elastic member at a predetermined level. With this configuration, the pedal device can adjust the reaction force applied to the driver pressing the pedal corresponding to the driver's driving propensity, thereby improving the operability and reducing the fatigue of the driver's ankle.