A ratchet-type tensioner capable of restricting setback of a plunger includes a ratchet mechanism that allows setback of the plunger by sliding a ratchet element in a disengaging direction to disengage ratchet teeth from rack teeth when a reaction force acts on the plunger as a result of excessive chain tension. The ratchet element is slidable in a ratchet-receiving hole, and an inclination suppressing structure that prevents the ratchet element from becoming skewed in the ratchet receiving hole to an extent such that its forward end contacts one side of the hole while its rearward end contacts the opposite sides of the hole.