PURPOSE: To improve the operability of a door holding device for holding a door at the opening position by automatically hold the door at the opening position without performing the operation for holding the door at the time of opening the door, and cancelling the door holding with the simple operation.

CONSTITUTION: A striker 5 is provided in a back door 3, and a lock assembly 8 is housed in a space between am inner plate 4a and an outer plate 4b forming a body 4. A rotating fork 15 to be engaged with the striker 5, which is inserted through an opening part 9a of a lock base 9 at the time of opening a door, for locking is provided in the inner surface side of the lock base 9 of the lock assembly fitted to the outer plate 4b. A lock cancelling lever 21 for cancelling the lock of the striker 5 by the rotating fork 15, which can be manually operated, is provided in the inner surface side of the lock base 9, and an operating part 24 of the lock cancelling lever 21 is pushed to cancel the lock of the striker 5.