A vehicular marker lamp including an auxiliary light emitting portion disposed near a tail/stop lamp (a main light emitting portion) having a red exterior appearance which is a lamp function color of the tail/stop lamp. The auxiliary light emitting portion is structured by a colorless and transparent light guide plate and a plurality of red light emitting diodes disposed so as to allow light from the light emitting diodes to be incident to the light guide plate so that when the tail/stop lamp is lit the light guide plate emits red light by the light which is incident from the light emitting diodes.