A medium loading device includes a support unit having shaft members mounted on both end portions of a roll paper and flange member and a loading portion where the roll paper with the support unit is loaded. The loading portion includes a rotary driving portion as a driving source to rotate the roll paper, a rotation shaft to transmit torque of the rotary driving portion to the roll paper via the shaft member, and an operation portion that moves the rotation shaft between a transmission position to transmit the torque to the roll paper and a non-transmission position not to transmit the torque to the roll paper. In an axial direction of the roll paper when the roll paper is loaded into the loading portion, the operation portion is disposed between the position where the shaft member is located when the roll paper is loaded and the rotary driving portion.