A collimator lens which converts, into convergent light, a light beam of divergent light emitted from a light source in which an emission wavelength changes according to temperature, comprising: a first face which faces the light source on a light path and on which the light beam is incident; a second face which is placed opposite to the first face and from which the light beam exits; and a diffractive structure which is formed on the second face; wherein in a case where divergent light emitted from a position P1 at a distance S1 from the second face enters the second face and imaging is performed at a position P2 at a distance S2 from the first face, in a temperature range of 0°C to 60°C and in a range of the emission wavelength of the light source which changes within the temperature range, and when a minimum value of a wavefront aberration of an image, which is generated at the position P2 by the divergent light emitted from the position P1 in a range of 0<S1/S2≤50, is WF1 at a temperature T1, and when a minimum value of a wavefront aberration of an image, which is generated at the position P2 when parallel light satisfying S1 = ∞ enters the second face, is WF2 at a temperature T1, the diffractive structure satisfies a relationship of WF1<WF2; characterizing in that; a emission wavelength of the light source is 788.0 nm and a refractive index of the collimator lens is 1.5242 at a temperature 20°C, in cases where R represents a curvature radius, k represents a Conic Constant, C represents an aspheric surface coefficient and D represents a diffraction coefficient, the first face has a shape which includes R=-90.000, k=-0.4143, C4=-1.052E-07, C6=1.495E-07, C8=1 761E-08 and C10=1.000E-09, the second face has a shape which includes R=-13.413, k =1.1858, C4=1.962E-05, C6=1.880E-05, C8=-1.626E-06, C10=4.937E-08, D2=-1.635E-02, D4=1.462E-05, D6=-8.457E-06, D8=7.647E-0 7 and D10=-2. 248E-08. a first face which faces the light source on a light path and on which the light beam is incident; a second face which is placed opposite to the first face and from which the light beam exits; and a diffractive structure which is formed on the second face; wherein in a case where divergent light emitted from a position P1 at a distance S1 from the second face enters the second face and imaging is performed at a position P2 at a distance S2 from the first face, in a temperature range of 0°C to 60°C and in a range of the emission wavelength of the light source which changes within the temperature range, and when a minimum value of a wavefront aberration of an image, which is generated at the position P2 by the divergent light emitted from the position P1 in a range of 0<S1/S2≤50, is WF1 at a temperature T1, and when a minimum value of a wavefront aberration of an image, which is generated at the position P2 when parallel light satisfying S1 = ∞ enters the second face, is WF2 at a temperature T1, the diffractive structure satisfies a relationship of WF1<WF2; a emission wavelength of the light source is 788.0 nm and a refractive index of the collimator lens is 1.5242 at a temperature 20°C, in cases where R represents a curvature radius, k represents a Conic Constant, C represents an aspheric surface coefficient and D represents a diffraction coefficient, the first face has a shape which includes R=-90.000, k=-0.4143, C4=-1.052E-07, C6=1.495E-07, C8=1 761E-08 and C10=1.000E-09, the second face has a shape which includes R=-13.413, k =1.1858, C4=1.962E-05, C6=1.880E-05, C8=-1.626E-06, C10=4.937E-08, D2=-1.635E-02, D4=1.462E-05, D6=-8.457E-06, D8=7.647E-0 7 and D10=-2. 248E-08.