To provide an imaging optical system having superior imaging performance over the full zoom range and having a wide viewing angle at the wide angle end and a high zoom ratio, by satisfactorily correcting chromatic aberration, and to provide an electronic imaging apparatus that uses the system.

In the electronic imaging apparatus having the imaging optical system and an imaging device, the imaging optical system has, in the order starting from the object side to the image side, a first lens group having positive refractive powers; a second lens group having negative refractive powers and an image-side lens group having positive refractive power, wherein a space between the first lens group and the second lens group changes at the zooming. A cemented optical element D is provided in the first lens group which is constituted so that a dioptric element (A) having positive refractive power is located between an object side optical element B and an image-side optical element C. The imaging optical system satisfies the conditional expressions (4-1), (4-2) and (4-3): (4-1) are νdA<30, (4-2): 0.54<θgFA<0.9, and (4-3): 0.387<(Tnglw(0.7)/Tbasw(0.7))/(Tngl(0)/Tbas(0))<0.525, respectively.