To overcome a problem in related art and to provide an easy-adhesive having an excellent adhesive property and an excellent adhesive durability for a solar cell rear surface protection sheet, a solar cell rear surface protection sheet, and a solar cell module formed by using the solar cell rear surface protection sheet. An easy-adhesive for a solar cell rear surface protection sheet according to the present invention exhibits a specific glass transition temperature, a specific number average molecular weight, and a specific hydroxyl value. Further, the easy-adhesive for a solar cell rear surface protection sheet contains a (meth)acrylic-based copolymer (A) that contains a carbon-carbon double bond in a side chain at a specific rate, and a polyisocyanate compound (B) at a specific rate.