A two-dimensional photonic crystal plane emission laser, comprising: a first conductive semiconductor layer and a second conductive semiconductor layer different from each other in a conductive type; an active layer which is sandwiched between the first conductive semiconductor layer and the second conductive semiconductor layer, and generates light by carrier impregnation; and a two-dimensional photonic crystal layer including a two-dimensional photonic crystal area having a two-dimensional periodic refractive index distribution, and a light reflecting area which is formed in a periphery of the two-dimensional photonic crystal area, in a direction along which the refractive index distribution is spread, the two-dimensional photonic crystal layer being adapted to select a wavelength of the light to be generated in the active layer, wherein a reflecting surface of the light reflecting area is disposed at such a position that, assuming that each of propagating directions of diffraction light residing in the two-dimensional photonic crystal is represented by a unit vector whose magnitude is 1, and one of the unit vectors is selected, a direction of a synthesized vector obtained by summing up all the unit vectors representing the propagating directions of diffraction light of an even number within an angle range less than 180 degrees around the one unit vector, is aligned with a normal direction of the reflecting surface, and the reflecting surface of the light reflecting area is further disposed at a distance from an end surface of the two-dimensional photonic crystal area where diffraction light in one of the propagating directions is reflected on the reflecting surface, a propagating direction and a phase of the reflection light, and a propagating direction and a phase of light in other one of the propagating directions are coincident with each other, respectively. a first conductive semiconductor layer and a second conductive semiconductor layer different from each other in a conductive type; an active layer which is sandwiched between the first conductive semiconductor layer and the second conductive semiconductor layer, and generates light by carrier impregnation; and a two-dimensional photonic crystal layer including a two-dimensional photonic crystal area having a two-dimensional periodic refractive index distribution, and a light reflecting area which is formed in a periphery of the two-dimensional photonic crystal area, in a direction along which the refractive index distribution is spread, the two-dimensional photonic crystal layer being adapted to select a wavelength of the light to be generated in the active layer, wherein a two-dimensional photonic crystal area having a two-dimensional periodic refractive index distribution, and a light reflecting area which is formed in a periphery of the two-dimensional photonic crystal area, in a direction along which the refractive index distribution is spread, the two-dimensional photonic crystal layer being adapted to select a wavelength of the light to be generated in the active layer, wherein a reflecting surface of the light reflecting area is disposed at such a position that, assuming that each of propagating directions of diffraction light residing in the two-dimensional photonic crystal is represented by a unit vector whose magnitude is 1, and one of the unit vectors is selected, a direction of a synthesized vector obtained by summing up all the unit vectors representing the propagating directions of diffraction light of an even number within an angle range less than 180 degrees around the one unit vector, is aligned with a normal direction of the reflecting surface, and the reflecting surface of the light reflecting area is further disposed at a distance from an end surface of the two-dimensional photonic crystal area where diffraction light in one of the propagating directions is reflected on the reflecting surface, a propagating direction and a phase of the reflection light, and a propagating direction and a phase of light in other one of the propagating directions are coincident with each other, respectively.