A vehicular turn signal lamp (BtL, BtR) comprising: a first lamp unit comprising a first light emitting unit and a first lighting circuit configured to turn on a plurality of light sources of the first light emitting unit on the basis of an input voltage, and a second lamp unit (2A, 2B) comprising a second light emitting unit and a second lighting circuit configured to turn on a light source of the second light emitting unit on the basis of the input voltage, wherein the first lighting circuit is configured: to sequentially turn on the plurality of light sources of the first light emitting unit in accordance with a timing signal generated by a timing generation circuit of the first lamp unit, and to output the timing signal to the second lighting circuit, and wherein the second lighting circuit is configured to start lighting of the light source of the second light emitting unit in accordance with the timing signal after the plurality light sources of the first light emitting unit have been sequentially turned on, wherein the first lighting circuit and the second lighting circuit are configured to turn on the corresponding light sources (10a, 20a) by receiving current (Iin) from a common electric power supply line, characterized in that: the second lamp unit (2A, 2B) further comprises a current consuming unit configured to consume a part of electric power to be supplied from the electric power supply line, wherein the first lighting circuit is configured to generate a state signal corresponding to a state of drive current flowing to the light sources of the first light emitting unit and to output a notification signal corresponding to the state signal to the second lighting circuit, wherein the second lighting circuit is configured to stop operation thereof or lower a current value of regulating current flowing to the current consuming unit when the notification signal indicates a lamp disconnection, and wherein the first lighting circuit is configured to output the timing signal through an output line for the notification signal. a first lamp unit comprising a first light emitting unit and a first lighting circuit configured to turn on a plurality of light sources of the first light emitting unit on the basis of an input voltage, and a second lamp unit (2A, 2B) comprising a second light emitting unit and a second lighting circuit configured to turn on a light source of the second light emitting unit on the basis of the input voltage, wherein the first lighting circuit is configured: to sequentially turn on the plurality of light sources of the first light emitting unit in accordance with a timing signal generated by a timing generation circuit of the first lamp unit, and to output the timing signal to the second lighting circuit, and to sequentially turn on the plurality of light sources of the first light emitting unit in accordance with a timing signal generated by a timing generation circuit of the first lamp unit, and to output the timing signal to the second lighting circuit, and wherein the second lighting circuit is configured to start lighting of the light source of the second light emitting unit in accordance with the timing signal after the plurality light sources of the first light emitting unit have been sequentially turned on, wherein the first lighting circuit and the second lighting circuit are configured to turn on the corresponding light sources (10a, 20a) by receiving current (Iin) from a common electric power supply line, characterized in that: the second lamp unit (2A, 2B) further comprises a current consuming unit configured to consume a part of electric power to be supplied from the electric power supply line, wherein the first lighting circuit is configured to generate a state signal corresponding to a state of drive current flowing to the light sources of the first light emitting unit and to output a notification signal corresponding to the state signal to the second lighting circuit, wherein the second lighting circuit is configured to stop operation thereof or lower a current value of regulating current flowing to the current consuming unit when the notification signal indicates a lamp disconnection, and wherein the first lighting circuit is configured to output the timing signal through an output line for the notification signal.