A medium transporting mechanism for transporting one of stacked media each of which has a hole is provided. A holder is provided on a movable transporting arm and holds the one of the media. A guide is provided in the transporting arm, the guide has a tapered surface that is inclined with respect to an axis of the guide. The tapered surface is configured to be brought into contact with an inner surface of the hole of the one of the media when the guide is inserted into the hole of the one of the media. The tapered surface includes a first surface on a tip end portion of the guide and a second surface on a base end portion of the guide. An inclined angle of the first surface with respect to the axis of the guide is greater than an inclined angle of the second surface with respect to the axis of the guide.