A terminal inserting device is provided, by which pulling force to pull a terminal fitting can be changed after the terminal fitting is inserted. The terminal inserting device includes an inserting unit and a control device. The inserting unit includes a front chuck unit and electric wire chuck unit, by which an electric wire is chucked and a terminal fitting attached to the electric wire is inserted into a terminal-receiving chamber of a connector housing. The electric wire chuck unit includes a pair of electric wire chucks, an insertion motor and an air cylinder. The electric wire chucks chuck the electric wire therebetween. The insertion motor pulls the terminal fitting after the terminal fitting is inserted in the terminal-receiving chamber. The air cylinder changes force which brings the pair of the electric wire chucks close to the connector housing so that pulling force to pull the terminal fitting can be changed. The control device controls the air cylinder to change the pulling force.