To improve the dimensional accuracy at the time of manufacturing a flexible print printing circuit base or a cover lay film by reducing the unevenness of the dimensional change rate generated by the moisture absorption of a polyimide film and the dimension change rate between lots.

A polyimide film is heated continuously and dried by infrared rays or an infrared ray heater continuously in a line to reduce the water content of the film to 0.1% or less, and a thermosetting bonding agent is applied on one face of the film, on which a metal foil is laminated, and the dimensional change rate of a film-metal foil laminate is set within ±0.05% both in the longitudinal direction and the width direction in the state of removing the metal foil on the laminate based on the measured value after the heat treatment under the condition of 150°C×30 minutes.