Method of manufacturing gas barrier film

A method of manufacturing a gas barrier film, comprising:

• feeding long lengths of a substrate;
• forming a silicon nitride film as said gas barrier film on said substrate by a capacitively coupled plasma-enhanced CVD technique in a film formation area while transporting said substrate in a longitudinal direction with a tension being applied to said substrate;
• measuring said tension applied to said substrate during transporting;
• and
• adjusting said tension applied on said substrate so that said tension becomes a predetermined value of not more than 100 [N/m] that does not cause deformation of said substrate softened by heat during film formation and prevents damage to said silicon nitride film formed on said substrate based on measurement results of said tension applied on said substrate,
• wherein gaseous raw materials using in said forming step of said silicon nitride film includes at least silane gas and ammonia gas, and
• wherein a ratio P/Q [W/sccm] is not less than 1 when a flow rate of the silane gas is denoted as Q[sccm] and a power input for generating a capacitively coupled plasma is denoted as P[W].