Clamps, and built-in electronic component unit

A clamp includes a base portion, a clamping portion and an urging member. The base portion is connected to a housing accommodating a device. The clamping portion is provided on a first face of the base portion, and clamps a mating member. The urging portion is provided on a second face of the base portion. The urging portion has elasticity, and urges the device in a case where the base portion is connected to the housing.