NOVELTY - An easily-adhesive base material (1) has base material (11) and the easily-adhesive coating layer (12) laminated on surface(s) of base material. The easily-adhesive coating layer is formed from the coating liquid containing polyvinyl butyral and the crosslinking agent having softening point at 150 degrees C or less. The easily-adhesive coating layer has a crosslinked structure of polyvinyl butyral and the crosslinking agent.    USE - Easily-adhesive base material is used for solar cell module containing solar cell protective sheet (all claimed).    ADVANTAGE - The easily-adhesive base material has excellent adhesiveness with respect to layer containing polyvinyl butyral, and provides protection sheet for solar module with excellent moisture resistance and weather resistance, and does not produce peeling with sealing material and sheet, and provides solar module with excellent durability and quality.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following:    (1) manufacture of easily-adhesive base material, which involves applying coating liquid containing polyvinyl butyral and the crosslinking agent having softening point at 150 degrees C to side of the base material, forming coating liquid layer, and drying;    (2) protection sheet for solar cell, which has easily-adhesive base material in which surface on the opposite side to base material in the easily-adhesive coating layer is a surface for connecting a sealing material;    (3) manufacture of protection sheet for solar cell, which involves heating thermoplastic material for forming the sealing material contact bonding layer at temperature more than softening point, supplying the heated thermoplastic material to the surface at the side of easily-adhesive coating layer of easily-adhesive base material, cooling thermoplastic material, and forming sealing material contact bonding layer; and    (4) solar module, which is provided with the sealing material including photovoltaic cell and protection materials are stacked on the main surface of the sealing material. The protection material has protection sheet for solar cells.    DESCRIPTION OF DRAWING(S) - The drawing shows the schematic sectional view of easily-adhesive base material.    Easily-adhesive base material (1)    Base material (11)    Easily-adhesive coating layer (12)