A vehicular headlamp comprising: an external case of a lamp constituted by a lamp housing with an opening and a cover that covers the opening of the lamp housing; and a lamp unit disposed in the external case, the lamp unit includes: a light source unit including a light source, a light source placing part in which the light source is placed, a reflector that reflects light emitted from the light source, and a heat sink that dissipates heat generated when the light source is driven; a fixation frame fixed in the external case; a movable frame supported on the fixation frame to be movable in one of a horizontal direction and a vertical direction in the external case; a lens unit including a projection lens that projects the light emitted from the light source and a lens holder that holds the projection lens and supported on the movable frame to be movable in the other direction of the horizontal direction and the vertical direction in the external case; a first aiming operating shaft configured to perform optical axis adjustment by moving the movable frame in the one direction of the horizontal direction and the vertical direction with respect to the fixation frame; and a second aiming operating shaft configured to perform the optical axis adjustment by moving the lens unit in the other direction of the horizontal direction and the vertical direction with respect to the movable frame, wherein the lens unit moves in the horizontal direction and the vertical direction with respect to the fixation frame in a state where a distance from a focus of the light emitted from the light source and reflected by the reflector to the projection lens is constant, characterized in that: the light source unit is fixed to the lamp housing in a state where the heat sink is positioned outside the external case. an external case of a lamp constituted by a lamp housing with an opening and a cover that covers the opening of the lamp housing; and a lamp unit disposed in the external case, the lamp unit includes: a light source unit including a light source, a light source placing part in which the light source is placed, a reflector that reflects light emitted from the light source, and a heat sink that dissipates heat generated when the light source is driven; a fixation frame fixed in the external case; a movable frame supported on the fixation frame to be movable in one of a horizontal direction and a vertical direction in the external case; a lens unit including a projection lens that projects the light emitted from the light source and a lens holder that holds the projection lens and supported on the movable frame to be movable in the other direction of the horizontal direction and the vertical direction in the external case; a first aiming operating shaft configured to perform optical axis adjustment by moving the movable frame in the one direction of the horizontal direction and the vertical direction with respect to the fixation frame; and a second aiming operating shaft configured to perform the optical axis adjustment by moving the lens unit in the other direction of the horizontal direction and the vertical direction with respect to the movable frame, wherein the lens unit moves in the horizontal direction and the vertical direction with respect to the fixation frame in a state where a distance from a focus of the light emitted from the light source and reflected by the reflector to the projection lens is constant, characterized in that: the light source unit is fixed to the lamp housing in a state where the heat sink is positioned outside the external case. a light source unit including a light source, a light source placing part in which the light source is placed, a reflector that reflects light emitted from the light source, and a heat sink that dissipates heat generated when the light source is driven; a fixation frame fixed in the external case; a movable frame supported on the fixation frame to be movable in one of a horizontal direction and a vertical direction in the external case; a lens unit including a projection lens that projects the light emitted from the light source and a lens holder that holds the projection lens and supported on the movable frame to be movable in the other direction of the horizontal direction and the vertical direction in the external case; a first aiming operating shaft configured to perform optical axis adjustment by moving the movable frame in the one direction of the horizontal direction and the vertical direction with respect to the fixation frame; and a second aiming operating shaft configured to perform the optical axis adjustment by moving the lens unit in the other direction of the horizontal direction and the vertical direction with respect to the movable frame, wherein the lens unit moves in the horizontal direction and the vertical direction with respect to the fixation frame in a state where a distance from a focus of the light emitted from the light source and reflected by the reflector to the projection lens is constant, characterized in that: the light source unit is fixed to the lamp housing in a state where the heat sink is positioned outside the external case.