The invention mainly aims to provide an economical filler layer for a solar cell module which is excellent in the adhesion property to a transparent front substrate and a backside protective sheet, does not worsen the working environments, and causes no adverse effect on a solar cell element or electrodes at the time of production. To accomplish the aim, the invention provides a filler layer for a solar cell module containing a silane-modified resin obtained by polymerizing an ethylenic unsaturated silane compound and a polyethylene for polymerization and characterized in that the filler layer for a solar cell module has a gel fraction of 30% or lower when the filler layer for a solar cell module is used in a solar cell module.