PURPOSE: To provide a locking device for a sunshade sheet which is good in appearance, simple in construction, and wind pressure proof.

CONSTITUTION: A locking rod 6 is installed at the free end of sunshade sheet 3, and a through hole 4 through which the locking rod 6 exposes partially is installed. A locking arm 10 is constructed by installing a grasping locking portion 12 at the tip end of a pair of arm rods 11 and installing a rotating projection 13 at the rear end. An arm bracket is constructed by installing a bearing 24 and a plurality of pairs of counter receiving holes 25 on a blade plate. With the arm rod 11 of locking arm 10 being compressed, the rotating projection 13 is engaged with the bearing 24, and the arm rod 11 is engaged with the counter receiving hole 25. The grasping locking portion 12 is passed through the through hole 4 to grasp the locking rod 6 downward, so that the sunshade sheet 3 is locked.