Child seat base

In order to provide a child seat base which provides the advantages of, for example, easy storage and carriage or easy height adjustment, a support leg (20) is mounted on the front side of a base body (1) of the child seat base. The support leg (20) can be attached to and detached from the base body (1) with a single motion. A foot section (40) is disposed at the bottom end of the support leg (20). The height of the support leg (20) can be adjusted in multiple levels and can be locked at each level by operating a foot-locking mechanism (50) of the foot section (40). A step (31) is provided between right and left step guide pipes (29). The height of the step (31) can be adjusted in multiple levels and can be locked at each level by operating a step-locking mechanism (30) of the step (31).