The present invention is to provide an optical transmitter that installs a laser diode and a circuit to control currents supplied to the laser diode, and reduces the size of the control circuit. The transmitter includes an LD, an LD-Driver, a monitor PD, and a control unit that outputs two data for the bias and modulation currents to the driver based on the photocurrent. The control unit provides a memory whose addresses correspond to the bias current, while a data for the modulation current is set within an address of the memory. Accordingly, the control unit adjusts the bias current so as to maintain the photocurrent constant and outputs the data for the modulation current to the driver by reading information stored in the address corresponding to the bias current.