Imaging optical system and imaging apparatus

An imaging apparatus comprising:

• an imaging optical system;
• and
• an imaging element that outputs an imaging signal corresponding to an optical image formed by the imaging optical system,
• the imaging optical system including, in order from a side of an object toward a side of an image plane
• a first lens group having positive refractive power,
• a second lens group having negative refractive power, and
• a final lens group having positive refractive power and being disposed on a side closest to the image plane, wherein
• upon focusing, the first lens group and the final lens group are each fixed, and the second lens group moves in an optical axis direction,
• the first lens group includes a first negative lens, a first cemented lens in which a negative lens and a positive lens are cemented, and a first air lens of negative refractive power sandwiched between the first negative lens and the first cemented lens, and
• the final lens group includes a second cemented lens in which a positive lens and a negative lens are cemented, a second negative lens, and a second air lens of negative refractive power sandwiched between the second cemented lens and the second negative lens.