PURPOSE: To provide a reel controller for a slot machine capable of accurately detecting a rotating pattern, reducing the number of parts and time for working for detection, reducing a fault and a reading error and furthermore, accurately stopping the pattern at a prescribed position of a reel window.

CONSTITUTION: A slit 2b corresponding to the pattern and a strobe hole 2a to detect the position are formed inside/outside an annular plate body 2 mounted on the side face of a rotary reel 1 in the circumferential direction. A photosensor 5a detects the strobe hole 2a, and a photosensor 5b starts to read the slit 2b at the timing of a detection signal. A read timing is set to the driving pulse of a stepping motor which drives the rotary reel 1. The slit is read and a pattern signal is outputted bit by bit every output of the driving pulse. When a player depressed a stop button, a stopping signal is outputted, however, when a strobe signal is outputted after the stopping signal is outputted, the rotary reel 1 stops at that time.