According to the invention, the thin film having the thickness controlled desirably can be easily formed using common semiconductor processes. Provided is a coating liquid for forming the porous film having an excellent dielectric property and mechanical property. Specifically, the coating liquid for forming a porous film comprises the condensation product obtained by condensation of one or more silicate compounds represented by the formula (X.sub.2O) .sub.i(SiO.sub.2).sub.j(H.sub.2O).sub.k and one more organosilate compounds represented by the formula (X.sub.2O).sub.a(RSiO.sub.1.5).sub.b(H.sub.2O).sub.c. Thus, the porous insulating film having sufficient mechanical strength and dielectric properties for use in the semiconductor manufacturing process can be manufactured.