A pivotal device for a support of an electric device includes a base and a flip module. The base includes a compartment. At least one first track is disposed in the compartment and is arcuate. At least one friction device is coupled to and movable relative to the base. The flip module includes a first sliding member and a second sliding member. The first sliding member is received in the compartment and is movable relative to the base along a contour of the at least one first track. The at least one friction device abuts the first sliding member. The first sliding member includes a second track. The second track is arcuate. The second sliding member is coupled to the first sliding member and is movable relative to the first sliding member along a contour of the second track.