The present invention provides a directly modulatable wavelength variable laser that enables long distance and large volume communication with a simple and compact configuration. The wavelength variable laser includes a semiconductor optical amplifier, an optical filter, and a frequency-amplitude converter. The semiconductor optical amplifier produces optical gain of the light signal. The optical filter configured by multi-stage connected waveguide ring resonators performs frequency modulation on the light signal. The frequency-amplitude converter performs amplitude modulation on the light signal frequency modulated in the optical filter.