An optical transmitting device includes: a laser diode to which a first or second driving current is provided; a controller to provide the laser diode with the first driving current to transmit an optical signal and with a plurality of second driving currents, to emit light, different from each other in magnitude during a stop of providing the first driving current; a measuring unit to measure an intensity of the light emitted by the laser diode; a calculator to calculate a threshold current of the laser diode, based on the intensities corresponding to the plurality of second driving currents measured by the measuring unit and magnitudes of the plurality of second driving currents; and a determination unit to determine a precursor of a sudden-death of the laser diode, based on an amount of variation in the threshold current calculated by the calculator during a specific period.