To realize optimum riding comfort on a running bicycle and improve versatility without worsening mountability onto the bicycle, while permitting the start of running without distributing a rider's effort to hold out.

This suspension unit has a damper body 1 energized in an elongating direction by a suspension spring 11, while one end is connected to the body side and the other end is connected to the wheel side. A reservoir 2 disposed outside of the damper body 1 and allowing the supply and discharge of oil to and from the damper body 1, when the damper body 1 is expanded and contracted; and a decrease-adjusting part 3 disposed in a passage 14a for communicating the reservoir 2 and the damper body 1 with each other, to adjust the quantity of passing oil in the passage by the input of an electric signal from the outside. In a first means, the reservoir 2 is interposed at the outer periphery of the decrease-adjusting part 3, and in a second means, the electric signal is outputted, on the basis of a detection signal from a sensor for detecting the tense state of a driving chain which is wound around a driving wheel.