In a method of producing a glass substrate including a laminate preparing step of laminating a glass film 1 having flexibility and a support glass 2 supporting the same, to prepare a laminate 3; a process step of forming an organic EL device 4 on the glass film 1 in the laminate 3, involving heating; and a peeling step of peeling off the glass film 1 on which the organic EL device 4 is formed from the support glass 2 to obtain a glass substrate 5, a heating step of heating the glass film 1 and the support glass 2 is executed before execution of the laminate preparing step, and the glass film 1 and the support glass 2 are laminated in the condition that they are heated at the time of execution of the laminate preparing step.