To obtain an olefin polymer having a high bulk density and excellent powder properties by using a specific solid catalyst (D) for olefin polymerization comprising a group IV transition metal compound catalyst component (A), an aluminoxane catalyst component (B) and a microparticulate organic compound/inorganic compound support (C).

Component A is represented by the formula: R1kR2lR3mR4nZr (wherein R1 is a cycloalkadienyl; R2 to R4 are each a cycloalkadienyl, an aryl, an alkyl, a cycloalkyl, an aralkyl, a halogen, H, ORa, SRb, NRc2 or PRd2; Ra, Rb, Rc or Rd are each a hydrocarbon group or silyl; k≥1, and k+l+m+n=4). Component B is represented by formula I or II (wherein R is a hydrocarbon group; and (m) is a number of 2 or greater). One half (0.5) to 500mg atom of Zr and 5-50,000mg atom of Al are present per 100g of component C. Component C used is made of a polyolefin or SiO2. Catalyst D has a mean particle diameter of 5-200μm and shows high polymerization activity in homopolymerization or copolymerization.