To provide normal-reverse rotating gear mechanism simple in mechanism with a small number of part items by providing a motive power gear with a partial external tooth gear and a partial internal tooth gear formed coaxially, and constituting in such a way that a driven gear is alternately meshed with the partial external tooth gear and partial internal tooth gear by unidirectional rotation of the motive power gear.

Normal-reverse rotating gear mechanism applied to loading mechanism of a disc regenerating device with two trays has a motive power gear 1 with a partial external tooth gear 1a and a partial internal tooth gear 1b provided around a rotary shaft. This motive power gear 1 has a tooth lacking part 1c formed between a circular arc angle at the time of looking at the partial external tooth gear 1a from the rotary shaft and a circular arc angle at the time of looking at the partial internal tooth gear 1b from the rotary shaft. A driven gear 2 having a rotary shaft in the constant position relation to the rotary shaft of the motive power gear 1 is arranged in a position to be meshed with the respective partial gears 1a, 1b. At the tooth lacking part 1c, the driven gear 2 is not meshed with any of the partial gears 1a, 1b, and the driven gear 2 is rotated normally and reversely with the tooth lacking part 1c in between by the unidirectional rotation of the motive power gear 1.