A drive circuit includes a bias current supply circuit for supplying a bias current to a light-emitting element and a modulated current supply circuit for supplying a modulated current to the light-emitting element, and has a first path through which the bias current flows, a second path including a path for supplying the modulated current to the light-emitting element from the modulated current supply circuit, through which a current returns to the bias current supply circuit through the modulated current supply circuit from the bias current supply circuit without going through the light-emitting element when the bias current flows, and a third path which is joined to the second path in the modulated current supply circuit and has an adjusting resistance before a junction, through which a current flows through the adjusting resistance to the bias current supply circuit when the bias current flows.
