Provided is an actuator including: a motor; a brake; a motor casing that accommodates a constituent member of the motor; and a brake casing that accommodates a constituent member of the brake. The motor casing and the brake casing are connected to each other, the brake includes a stator having a coil and a coil case, and a friction plate, a minimum outer diameter of the coil case is 70 mm or less, and a value obtained by dividing a distance from a first end surface of the friction plate on a side farthest in an axial direction from the coil case to a second end surface of the coil case on a side opposite to the first end surface by the minimum outer diameter is 0.2 or less.