Disclosed herein are a brake device of an in-wheel motor and an in-wheel motor including the same. The brake device of an in-wheel motor includes a brake drum part fixed to one surface of a rim of an in-wheel motor and having at least one hole, and at least one pin pushing/pulling driver installed inside the brake drum part in a radial direction thereof and configured to push or pull a pin, which is insertable into the hole according to an input of a braking signal of the in-wheel motor, toward or from the hole. The brake drum part includes a disc body having a hollow and an outer wall, wherein a shaft of the in-wheel motor is disposed to pass through the hollow and the outer wall is fixed to the rim, and a circumferential protrusion protruding a predetermined length in a direction spaced apart from the disc body to the rim and having the hole in the circumferential protrusion. When the braking signal is input, a braking force is rapidly applied to the in-wheel motor, and also the braking force is constantly maintained using a mechanical mechanism even when a supply of electric power is cut off on an inclined road and the like such that safety can be improved.
