A small, compactly configured reference position detection device 170 for a rotary transfer mechanism includes a rotary member 130 that can rotate through a rotational angle less than one revolution from a first rotational position past a second rotational position and reference position to a third rotational position; a detection flag disc 151 that can move in a range from a first position past a detection position to a second position; a detector 162 that detects the detection flag passing the detection position, and a flag moving mechanism. The flag moving mechanism can move the detection flag disc 151 tracking the rotary member 130. The position of detection flag disc 151 movement when passing the reference position of the rotary member 130 is the detection position.