To solve the problem that a user of Nordic skis falls easily since the skis are separated from each other in a truncated chevron shape because side flow of the skis cannot be prevented by recessed grooves formed at a right angle to their advancing direction so as to prevent the skis from slipping in a direction reverse to the moving direction though reverse movement of the skis can be prevented by the grooves.

While preventing the reverse movement of the skis by increasing resistance to the direction reverse to the moving direction by forming flaky recessed grooves on the ski surfaces of the skis, the side flow of the skis is prevented by increasing resistance to the direction at a right angle to the moving direction by arraying the flaky recessed grooves facing backward obliquely from the advancing direction. In addition, since the flaky recessed grooves come into contact with projecting parts on a snow surface at an oblique angle due to the oblique flaky recessed grooves, the redistance to the advancing direction is reduced and the skis move amoothly. Thus, a falling accident is prevented.