Disclosed is a process for continuously mixing two liquid components, whose one liquid component is a two-liquid curing type resin which comprises continuously supplying one liquid component under stirring into a mixing container and pouring the other liquid component into said container by pushing open a needle forcibly provided to a check valve, the improvement wherein said needle is pushed open with a non-curing liquid, thereafter, a curing liquid is poured into said mixing container. According to the present invention, when, for example, a polyamide acid and a curing agent are caused to mix and react with each other, a transparent polyimide mixed uniformly is obtained and high quality molded articles of polyimide are provided therefrom.