Medium transport apparatus and image reading apparatus

A medium transport apparatus comprising:

• a medium transport roller pair including a stationary-side roller disposed on a medium transport path along which a medium is transported and a moving-side roller formed so as to be able to come into contact with, or separate from, the stationary-side roller;
• a roller support member formed so as to support the moving-side roller and be able to assume a first state in which the roller support member causes the moving-side roller to be in contact with the stationary-side roller and a second state in which the roller support member causes the moving-side roller to separate from the stationary-side roller;
• an urging device urging the roller support member toward the first state;
• a cam formed so as to engage the roller support member and shift the roller support member from the first state to the second state against an urging force of the urging device;
• and
• an external force providing portion to exert, while the roller support member is shifted by the cam to be in the second state, a third external force on the roller support member in a direction for restraining warping that is generated in the roller support member by a first external force that the cam exerts on the roller support member and by a second external force that the urging device exerts on the roller support member.