Copolymer rubber, rubber composition and rubber molded product

3-20 5The invention provides a copolymer rubber excellent in processability in kneading and processability in extrusion; rubber compositions containing the rubber; and crosslinked moldings of the compositions excellent in sealing properties and shape retention. A random copolymer rubber of ethylene (A), a Cα-olefin (B) and a nonconjugated polyene (C) which satisfies the following requirements (1) to (5): (1) the structural units (A) and (B) are contained at an (A)/(B) molar ratio of 40/60 to 95/5, (2) the structural unit (C) content is 0.01 to 5% by mole, (3) the limiting viscosity [η] is 1.0 to 5.0 dl/g as determined in decahydronaphthalene at 135°., (4) the Mw/Mn is 1 to 8, and (5) the P value is 0.46 to 1.00 as defined by formula (1): P=Ln(limiting viscosity [η])−5.0×10×η*(10) (1) (wherein Ln is a natural logarithm; and η*(10) is viscosity (Pa·sec) as determined at 190° C. and at 10 rad/sec.