The present photosensitive resin composition 2 comprises a polyamic acid
resin 4, a photosensitive agent, a dispersible compound 3 dispersible in
the polyamic acid resin 4, and a solvent. The porous resin is obtained by
removing the solvent from the photosensitive resin composition 2 to form
a composition in which the dispersible compound 3 is dispersed in the
polyamic acid resin 4, removing the dispersible compound to make the
composition porous, and curing the porous photosensitive resin
composition. The porous resin enables forming a fine circuit pattern and
has a low dielectric constant and, when used as an insulating layer of a
circuit board, brings about improved high frequency characteristics.