Series load control apparatus and marker light apparatus

According to one embodiment, a plurality of first saturable units respectively include input sections connected to an output side of a constant current power supply apparatus in series to one another and respectively supply outputs to loads corresponding thereto. A second saturable unit includes an input section and an output section, the input section being connected to the input sections of the first saturable units in series. An abnormality detecting unit monitors a state of the load of at least one of the first saturable units, closes the output section of the second saturable unit during normal time, and opens the output section of the second saturable unit during abnormal time.