To provide a motor which can be started smoothly, even in low- temperature atmosphere, and a roller having this motor within.

The roller 1 with a built-in motor is one, where a motor 3 and a reduction gear 4 are built in the roller body 2. For the motor 3, a stator 13, a rotor 14, a position detector 15, and a thermistor 16 being a temperature measuring member are built in the motor body 12. A drive controller 19, which controls the drive of the motor 3, is annexed to the motor 3. The drive controller 19 is classified roughly into a control circuit part 20, a magnetic pole detection circuit 21, and a current-switching part 22. A current applicant means 35 is annexed to the current-switching part 22. In the stator 13, a lubricant such as grease is kept at low viscosity, since it is heated by the DC current supplied from the current application means 35 when the roller 1 is stopped with a built-in motor. Therefore, the roller 1 with a built-in motor can start smoothly, even under low-temperature atmosphere.