A small-sized motor operated valve is disclosed that has high output and high resolution by housing a reduction gear together with a rotor in a single can. A valve shaft 32 having a valve member 30 is inserted to a motor operated valve body 10. A rotor 170 is disposed inside a can 100 attached to the body 10, and inside the rotor 170 is housed a reduction gear 200. The output of the rotor is input to a sun gear 220 and transmitted to planetary gears 230. The planetary gears 230 are engaged both with the fixed gear 250 and the output gear 260, and the output gear 260 is driven at reduced speed by a large reduction ratio. The output of the output gear 260 is transmitted via a driver 300 to a screw shaft 320, where it is converted into a linear movement and transmitted to the valve shaft 32.