A lamp includes a housing, a heat dissipating plate, a circuit unit, and a heat distributing unit. The housing includes a housing body surrounding an axis and having an opening. The heat dissipating plate is disposed in the housing body and has a peripheral portion contacting the housing body. The circuit unit is disposed in the housing body, and includes a base plate coupled to the heat dissipating plate, and a light emitting unit mounted to the base plate opposite to the heat dissipating plate. The heat distributing unit is disposed in the housing body, and includes a heat conducting bar coupled to the heat dissipating plate opposite to the circuit unit, and further coupled to a heat distributing plate opposite to the heat dissipating plate. The heat distributing plate has a plate periphery contacting the housing body.