To provide a manufacturing method of a film capacitor element and a manufacturing device capable of sufficiently improving an insulation resistance value of a film capacitor element composed of a structure in which a film is laminated in a roll shape.

A manufacturing method of a film capacitor element C includes a moisture removal step of removing the moisture contained in the air between films laminated in a roll shape. The moisture removal step comprises: a first step of raising the temperature of the film capacitor element C to a prescribed temperature; a second step of vacuum-drying the film capacitor element C whose temperature was raised in the first step; and a third step of pressing the film capacitor element C whose temperature was raised in the first step.