The invention relates to a clamping device (1) for a non-skid chain, comprising a housing (2) and an actuation member which has a lock-in position in which a clamping strand which can be pulled into the housing through a housing opening can be blocked in the opposite direction to the clamping direction; and a release position in which the block is released. Said clamping strand is connected to a coiling roll (4) inside the housing, said coiling roll being prestressed in the winding up direction and being mounted in such a way that it can rotate about its axis. A ratchet wheel with at least one associated, spring-loaded detent pawl (6) and a second ratchet wheel (7) with an associated, spring-loaded detent pawl (8) are provided on the coiling roll and the two ratchet wheels are interconnected in a rotationally fixed manner. The blocking directions of the ratchet wheels are opposed and the spring-loaded detent pawls of the first or second ratchet wheel can be engaged with the corresponding ratchet wheels alternately by means of a common actuating mechanism (3).