To provide a vehicular folding type door capable of detecting catch of foreign matters caused in a connection part of an upper side door and a lower side door.

A back door 12 is opened by folding in the center so that the connection part CN of the upper side door 15 and the lower side door 16 projects outside a vehicle body, by rotatably connecting an upper part of the lower side door 16 to a lower part of the upper side door 15 having an upper end part rotatably connected to the vehicle body side, and has a garnish 21 rotatably connected to the upper side door 15 and covering the connection part CN from the outside of the vehicle body over the total length in the width direction, a torsion spring 22 for energizing the garnish 21 to a predetermined initial position, and a switch 23 for detecting the movement of the garnish 21 from the initial position.