A child restraint device comprising: a backrest (10) arranged along the back section of a vehicle seat and having a backrest surface (10a) extending in the vertical direction; a seat section (9) connected to the bottom section of the backrest so as to be swingable between a usage position and a stowed position, and configured so as to extend in front of the backrest surface in the usage position and extend along the backrest surface behind the backrest surface in the stowed position; top-side position regulating sections (16) that regulate the top-side position of a pair of shoulder belts (30) and which are each provided in left and right sections in an upper section of the backrest surface; bottom-side position regulating sections (17) that regulate the bottom-side position of a pair of shoulder belts each provided below the top-side position regulating sections in the backrest surface or in left and right sections of the seat section (9); an upper body belt section (12) including the pair of shoulder belts that extend from the top-side position regulating sections to the bottom-side position regulating sections, and a pair of tongue plates (31) each attached to the pair of shoulder belts such that each of the pair of shoulder belts are inserted therethrough; side guard sections (14) that extend forward from the left edge and right edges sections of the bottom section of the backrest; and a crotch belt section (13) extending from a crotch belt attachment section (40) provided in the center section of the front end section of the seat section, and having provided in the front end section thereof a pair of tongue plates and a detachable buckle (35).