To prevent a front wheel from carelessly turning in a middle state of folding up a baby carriage.

A collapsible baby carriage comprises a caster mechanism having a caster rotary member rotatably held around the turning axis extending in the vertical direction with respect to a caster holding member and journaling a front wheel (12) and capable of directionally turning the front wheel and a caster lock member provided in the caster holding member, regulating rotation of the caster rotary member by engaging with the caster rotary member in a first position and allowing the rotation of the caster rotary member by separating from the caster rotary member in a second position, and is constituted so that the caster lock member is put in the second position in a deploying state by interlocking with a form change in the baby carriage of changing a form in a folding-up state from the deploying state and the caster lock member is put in the first position in a folding-up middle state being a middle state of the form change.