In a wide-angle optical system for a solid image pickup element, an image pickup lens 2 is a biconvex lens, and its surface closer to an image surface is being formed into such an aspherical shape that the positive refractive power is weaker at a location more spaced in a diametrical direction apart from an optical axis. Further, the image pickup lens 2 satisfies the following condition expression (1):

1.3|r₁/r₂|0.8  (1)

wherein r₁ is a radius of curvature of a surface of the image pickup lens closer to an object, and r₂ is a radius of curvature of the surface of the image pickup lens closer to the image surface. Thus, the distortion can be corrected appropriately.