To provide an inner cable unslacking device capable of tightening slack of an inner cable by smooth operation and keeping its tensile force so as to prevent the inner cable from returning into its loosened condition by a simple mechanism.

This unslacking device 1 is composed of a core 2 like a circular column provided with one stepped engaging part 2c constituted by connecting a plurality of steps 2d arranged at substantially equal interval in the axial direction or more, a cylindrical housing 3 provided with a locking protruding bar 3d having a front end face engaging with a step 2c of the engaging part 2c of the core 2 on an inner peripheral face, a cylindrical spacer 4 arranged at the outer periphery of the housing 3 to connect its front end with the core 2, and an energizing member 5 for energizing the spacer 4 forward for the housing 3.