To provide a bicycle with a child seating device which dose not hinder a motion for getting a child on/off a child seat and riding of a rider, in a bicycle with a child seat disposed in rear of a handlebar post.

A child seat 31 is disposed freely to slide forward and backward over from a front position for seating in travelling, in which a seating part 31a of the child seat 31 approaches or abuts on the handlebar post 14, to a rear position for getting on/off, in which the seating part 31a of the child seat 31 separates from the handlebar post 14. With this structure, when getting a child on/off the child seat, the child can be easily gut on/off in a state that legs of the child hardly abut on the handlebar post 14 and a handlebar 13 by switching the child seat 31 to the rear position for getting on/off.