PURPOSE: To obtain the loupe which has about ×4.5 power and also has various aberrations compensated excellently and is inexpensive by making the radii of curvature of three positive lenses common.

CONSTITUTION: This loupe consists of a 1st biconvex positive lens 11, a 2nd biconcave negative lens 12, a 3rd biconvex positive lens 13, and a 4th positive lens 14 in order from the object side, and the surface shapes of the six surfaces of the 1st, 3rd, and 4th three positive lenses 11, 13 and 14 are composed of a combinations of absolute values of 53 kind of radii of curvature and made common. Further, respective conditional expressions n2<1.75, ν<35, 0.9f<r7<3rf, and (n1+n3+n4)/3<1.65 are satisfied. Here, n1 is the refractive index of the 1st lens 11, n2 the refractive index of the 2nd lens 12, n3 the refractive index of the 3rd lens 13, ν2 the Abbe number of the 2nd lens 12, r7 the radius of curvature of the 1st surface of the 4th lens 14, and (f) the focal length of the whole system. The three positive lenses 11, 13, and 14 are composed with a combination of 2 kinds of radius of curvature or one kind of radius of curvature to further reduce the cost.