Disclosed herein are a wheel assembly and a robot cleaner including a main body and a wheel assembly coupled to the main body to guide movement of the main body. The wheel assembly has a rotation arm including a first end portion rotatably mounted on the main body, a drive wheel rotatably installed on a second end portion of the rotation arm opposite the first end portion, and an elastic member including a first end installed at the main body and a second end vertically moveably installed at the rotation arm opposite the first end, such that a reduction degree of a contact force due to a descent of the drive wheel.