A web conveyance mechanism for conveying a band-type web includes: a side guide provided on one end side of the web in its width direction that guides one end of the web in the width direction which abuts on the side guide and that serves as a positional reference in the width direction for the web; an abutting unit that pushes the web to the side guide and adjusts an abutting force with which the web pushes the side guide; a measuring unit that measures the abutting force with which the web abutting on the side guide pushes the side guide; and a controller that adjusts the abutting unit so as to obtain a desired abutting force based on a result of detection by the measuring unit.