An optical transmitter includes a plurality of VCSELs (vertical cavity surface emitting laser) that convert an electrical signal into an optical signal and transmit the converted optical signal. The optical transmitter measures a time for each of the VCSELs of transmitting an optical signal. Then, the optical transmitter assigns an electrical signal, indicating information to be transmitted, to one or more VCSELs, out of the VCSELs, other than a VCSEL of which a cumulative time measured is more than a predetermined threshold.