A wavelength conversion device comprising: a gain medium including quantum dots; a first optical system for injecting a signal light having a wavelength to the gain medium; a tunable laser having a tunable oscillation wavelength; a second optical system for injecting a laser light formed by the tunable laser to the gain medium; the wavelength conversion device further comprising a tunable filter for selectively extracting output light generated from optical four wave mixing in the gain medium, the tunable filter having a tunable frequency at which it extracts the output light, wherein the first optical system includes a first optical amplifier for amplifying the signal light with a first amplification factor (α), wherein the second optical system includes a second optical amplifier for amplifying the laser light with a second amplification factor (β), the wavelength conversion device further including a control apparatus for controlling the first and second optical amplifiers (41, 43), the control apparatus altering the first and second amplification factors (α, β) based on the absolute value of the difference (Δf) between the wavelength of the signal light and a wavelength of the laser light, wherein the control apparatus is configured to compensate for the decrease of the output light power associated with the increase in the difference (Δf); an optical coupler for coupling the signal light, after it has passed through the first optical system, and the laser light, after it has passed through the second optical system; a polarization beam splitter for dividing the light outputted by the optical coupler and supplying it by optical paths to the gain medium; an optical circulator, disposed between the optical coupler and the polarization beam splitter, for extracting the output ligth. a gain medium including quantum dots; a first optical system for injecting a signal light having a wavelength to the gain medium; a tunable laser having a tunable oscillation wavelength; a second optical system for injecting a laser light formed by the tunable laser to the gain medium; the wavelength conversion device further comprising a tunable filter for selectively extracting output light generated from optical four wave mixing in the gain medium, the tunable filter having a tunable frequency at which it extracts the output light, wherein the first optical system includes a first optical amplifier for amplifying the signal light with a first amplification factor (α), wherein the second optical system includes a second optical amplifier for amplifying the laser light with a second amplification factor (β), the wavelength conversion device further including a control apparatus for controlling the first and second optical amplifiers (41, 43), the control apparatus altering the first and second amplification factors (α, β) based on the absolute value of the difference (Δf) between the wavelength of the signal light and a wavelength of the laser light, wherein the control apparatus is configured to compensate for the decrease of the output light power associated with the increase in the difference (Δf); an optical coupler for coupling the signal light, after it has passed through the first optical system, and the laser light, after it has passed through the second optical system; a polarization beam splitter for dividing the light outputted by the optical coupler and supplying it by optical paths to the gain medium; an optical circulator, disposed between the optical coupler and the polarization beam splitter, for extracting the output ligth.