To provide a chain tensioner device absorbing a change of span length of a chain due to rotation of a sprocket so that a vibration of the chain can be reduced.

A chain guide 10 supported to freely swivel to a loosened side chain 3a of a chain 3 linked over between sprockets 1, 2 is oppositely provided, a swivel side end part of this chain guide 10 is pressed by a plunger 21 of a chain tensioner 20, to tense the loosened side chain 3a. A pad 30 having a non-linear spring characteristic is mounted in a plunger contact part of the chain guide 10, so as to absorb a change of span length of a return side chain 3a due to rotation of the sprocket 1 by this pad 30, a vibration of the return side chain 3a is reduced.