I'd like to apply electric motor with small size.
My application is rotating screw with 1 deg accuracy and under 1kgfcm torque.
Which type of motor is best choice?
If the screw is about to turn more than 360 degrees then you should use a stepper motor. The accuracy you need is difficult to be achieved by other motor types.
Some stepper motors are able to move in very small increments, like 0.9 degrees per step or 400 steps per revolution.
Most stepper motors, move 1.8 degrees per step, or 200 steps per revolution.
To achieve 1 degree accuracy you may also use a 200 step motor with micro-stepping, which is a technique to hold the shaft at some point between two steps by calculating and energizing adjacent coils at various percentage. This can be done by most stepper controllers.
Be aware that micro-stepping draws current from more than one coil at the same time and also affects the torque.
As for the torque, you just have to select a stepper size that has enough force.