To calculate a road surface friction coefficient corresponding to the condition of a road surface irrespective of the traveling state of a vehicle in a road surface friction coefficient calculation device.

The road surface friction coefficient calculation device is equipped with: a longitudinal acceleration detection means 1 detecting longitudinal acceleration acting on the vehicle; a clocking means 2 measuring regular traveling duration in a state where the longitudinal acceleration is not detected in the vehicle; a braking/driving force imparting means 3 imparting minute braking/driving force to the vehicle for a second predetermined time when the regular traveling duration measured by the clocking means 2 becomes a first predetermined time or more; and a road surface friction coefficient calculation means 4 calculating the friction coefficient of a road surface on which the vehicle travels after the impartation of the minute braking/driving force. The clocking means 2 resets the traveling elapsed time when the friction coefficient is calculated by the road surface friction coefficient calculation means 4 and starts measuring the regular traveling duration again. The friction coefficient of the road surface is periodically calculated in every predetermined time thereby.