METHOD FOR PRODUCING POLYOLEFIN

There is provided a method comprising a step of feeding a polyolefin powder having a catalytic activity into a gas phase polymerization vessel in which there is a polyolefin powder and through which a gas comprising an olefin is being circulated, thereby commencing polymerization of an olefin, wherein the following formula (1) is satisfied: 0.5 < ² / ±B < 24.0 in the above formula (1), ± represents the median diameter (unit: µm) of the catalytically active polyolefin powder to be fed into the vapor phase polymerization vessel, ² represents the median diameter (unit: µm) of the polyolefin powder that is contained in the vapor phase polymerization vessel before the feeding of the catalytically active polyolefin powder into the vapor phase polymerization vessel, and B represents the linear gas velocity (unit: m/sec) of the gas containing an olefin within the vapor phase polymerization vessel.