A wavelength selection filter, a wavelenth selection laser, and a tunable laser for suppressing adverse effects of non-selected light when selected light is obtained by the wavelength selection filter. A linear polarizer is arranged on a side of the wavelength selection filter from which incoming light enters, and a first faraday element and a second faraday element arranged at respective locations between the linear polarizer and the wavelength selection filter, and between the wavelength selection filter and a reflection mirror for reflecting light having passed through the wavelength selection filter. After incoming light passes through a linear polarizer, selected light passes through the wavelength selection filter and is reflected by the reflection mirror, while non-selected light is reflected by the wavelength selection filter. The selected light and the non-selected light differ in the number of times they pass through faraday elements before they return to the linear polarizer.