The object of the present invention is to provide a production process of a microfluidic device in which a porous resin layer, which is capable of optimally fixing a large amount of enzyme, antigen or other protein or catalyst on the inner surface of a minute channel of a microfluidic device without obstructing said channel, is formed at a uniform thickness on the surface of said channel.In the present invention, by preliminarily forming a porous resin layer having a large number of pores in its surface on a substrate, and forming an indentation having a porous resin layer on its bottom surface by using an activating energy beam-curable composition on said porous resin layer, followed by forming a channel by adhering a member serving as a cover to said indentation, a porous resin layer can easily be formed at a uniform thickness on the surface of said channel.