PURPOSE: To prevent leading of a molded form through a mold and obtain excellent molded form by using a cavity mold in which a surface in contact with the from is coated with a heat insulator.

CONSTITUTION: A method for manufacturing a crosslinked polymer molded form comprises the steps of mixing monomer liquid having metathesis polymerizable cycloolefin catalytic component of metathesis polymer catalyst base with monomer liquid having metathesis polymerizable cycloolefin containing activator component of metathesis polymer catalyst base, and casting the mixture in a mold to polymerize it, wherein a surface in contact with the form uses a cavity mold coated with heat insulator. The insulator dissipates irregular heat due to self-heat generation at the time of polymerizing out of a system while controlling it on the surface of the mold. The insulator desirably includes, for example, thermally cured organic resin selected from tetrafluoroethylene base, epoxy base, polyester base and phenol base durable against heat generation of the metathesis polymerization. An additive desirably includes, for example, filler, pigment, antioxidant, light stabilizer, etc.