To provide a sealing material composition for solar cell module which can impart excellent adhesion for both metal and glass to a sealing material sheet for solar cell module while using a polyethylene-based resin, and to provide a sealing material sheet for solar cell module using the same.

The sealing material composition for solar cell module is composed of a polyethylene-based resin having a density of 0.900 g/cm³ or less. The sealing material sheet for solar cell module uses the sealing material composition. The polyethylene-based resin composing the sealing material composition contains a copolymer produced by copolymerization of at least α-olefin and ethylene unsaturated silane compound as a comonomer, and also contains a silane coupling agent having an epoxy group or a mercapto group.