To provide a child seat connecting structure and a connecting member to be easily attached to/detached from a fixed body, capable of tensioning the webbing of the connecting member when the distance between the fixed body and the upper part of a child seat is short.

The child seat 20 is mounted on a seat 10, and the arm 26 is latched to a clamp bar 16 on the vehicle side. The upper part of the child seat 20 is connected to a tether anchor 38 of a rear plate 18 via the webbing 30, an adjuster 52 and a hook 54. The adjuster 52 and the hook 54 are integrated.