PURPOSE: To surely detect a gravel road, sandy road and damp road having the same degree of coeffincient of friction on the road surface.

CONSTITUTION: A vertical motion detecting part 14e in a road surface detecting unit 14 of a road surface detecting apparatus for detecting the road surface condition on which an automobile 10 travels compares a reference voltage value V1 from a reference calculating section 14d based on car body speed detected by a vehicle speed sensor 13 with a detecting value of a vertical G sensor 11 to detect the vertical variation. A pressure detecting section 14f compares reference voltage values V2, V3 from the reference calculating section based on the car body speed with the detecting value of a pressure sensor 12 to detect the size of pressure. According to these detecting results a road surface detecting section 14g detects discriminatingly a sandy road, damp road and gravel road having the same degree of coefficient μ of friction.