A single-chain-end functionalized polyolefin and method of producing the same. The polyolefin is represented by the following general formula (I): P—X  (I) wherein X is a group containing at least one element selected from oxygen, sulfur, nitrogen, phosphorus and halogens, P represents a polymer chain made mainly of an olefin composed only of carbon and hydrogen atoms, and X is bonded to a terminal of P, wherein the molecular weight distribution (Mw/Mn) obtained by gel permeation chromatography (GPC) is from 1.0 to 1.5.