A light emitting element driving device comprising: a first driving circuit arranged to be capable of supplying power to a light emitting element connected to an output terminal of said first driving circuit in a first mode, and to be disabled to supply power to the light emitting element connected to the output terminal of said first driving circuit in a mode other than the first mode; characterized in that it comprises a second driving circuit arranged to be capable of supplying power to a light emitting element connected to an output terminal of said second driving circuit in a second mode; a first abnormality detection circuit arranged to detect an abnormality of the light emitting element connected to the output terminal of the second driving circuit at least in the second mode; a bypass path connecting the output terminal of the first driving circuit to the output terminal of the second driving circuit; and a first switching portion disposed in the bypass path so as: - to make the bypass path into a conductive state to connect together the light emitting element connected to the output terminal of the first driving circuit and the output terminal of the second driving circuit when an abnormality is detected by the first abnormality detection circuit, and - to make the bypass path into a cutoff state not to connect together the light emitting element connected to the output terminal of the first driving circuit and the output terminal of the second driving circuit when an abnormality is not detected by the first abnormality detection circuit, wherein the first driving circuit is capable of supplying power to the light emitting element connected to the output terminal of said first driving circuit in the first mode even when the bypass path is in the cutoff state. a first driving circuit arranged to be capable of supplying power to a light emitting element connected to an output terminal of said first driving circuit in a first mode, and to be disabled to supply power to the light emitting element connected to the output terminal of said first driving circuit in a mode other than the first mode; characterized in that it comprises a second driving circuit arranged to be capable of supplying power to a light emitting element connected to an output terminal of said second driving circuit in a second mode; a first abnormality detection circuit arranged to detect an abnormality of the light emitting element connected to the output terminal of the second driving circuit at least in the second mode; a bypass path connecting the output terminal of the first driving circuit to the output terminal of the second driving circuit; and a first switching portion disposed in the bypass path so as: - to make the bypass path into a conductive state to connect together the light emitting element connected to the output terminal of the first driving circuit and the output terminal of the second driving circuit when an abnormality is detected by the first abnormality detection circuit, and - to make the bypass path into a cutoff state not to connect together the light emitting element connected to the output terminal of the first driving circuit and the output terminal of the second driving circuit when an abnormality is not detected by the first abnormality detection circuit, - to make the bypass path into a conductive state to connect together the light emitting element connected to the output terminal of the first driving circuit and the output terminal of the second driving circuit when an abnormality is detected by the first abnormality detection circuit, and - to make the bypass path into a cutoff state not to connect together the light emitting element connected to the output terminal of the first driving circuit and the output terminal of the second driving circuit when an abnormality is not detected by the first abnormality detection circuit, wherein the first driving circuit is capable of supplying power to the light emitting element connected to the output terminal of said first driving circuit in the first mode even when the bypass path is in the cutoff state.