There are provided an imaging optical system and imaging equipment, which are compatible with a solid-state imaging device having a size of ½ inches or less and which include an optical system having a small size and lightness in weight and also having an excellent mass productivity and a low cost while keeping optical performance at a wide field angle, for example, at a total angle of view of 80 degrees or more. When predetermined conditions are satisfied for a plurality of lenses constituting the imaging optical system, the absolute value of power of each lens group is suppressed to be small, and thus the generation of aberration is suppressed and a preferable aberration is obtained.