To provide an olefin polymerization catalyst having excellent particle properties which excels in polymerization activity and can give a polymer having excellent polymer properties at a low cost, and a process for producing a polyolefin polymer.

The olefin polymerization catalyst is composed of a metallocene compound and a cocatalyst carrier, and the supporting ratio of the metallocene to the cocatalyst carrier is 0.60 wt.% to 20 wt.%, and simultaneously, the amount of a transition metal derived from the metallocene compound to be extracted with n-heptane at 20°C is less than 0.30 wt.% of the amount of the transition metal of the metallocene compound supported on the cocatalyst carrier.