PURPOSE: To provide a crosslinked PVC article capable of preventing leakage of plasticizers, etc., providing controlled release of substances such as pesticides and having such a gradient crosslinking density as to have a high crosslinking density on the outer surface and a low or none crosslinking density at the bulk of the product.

CONSTITUTION: A PVC product is immersed at a temperature of 60-90°C in an aqueous solution of a crosslinking substance (e.g. sodium diethyldithiocarbamate) being a dithiocarbamate of formula I (wherein R2 is an alkyl optionally substituted with hydroxyl or an acyloxy or the like; and R2 is H or R1; or the like) or a difunctional or trifunctional thiol compound of formula II or III (wherein R is an alkyl, an aryl or the like) and a phase transfer catalyst being a quat. ammonium salt or a tert. alkylphosphonium salt (e.g. tetrabutylammonium chloride).