PURPOSE: A PP resin molded article containing a specific amount of carbon black is plasma-treated and then painted to give a painted article having excellent peeling strength and moisture resistance of the coating film and useful for outdoor use. The paintability of a PP resin can be improved remarkably by this process.

CONSTITUTION: A molded article of a PP resin obtained by compounding (A) 100pts.(wt.) of a resin composed of (i) 100pts. of a PP resin, (ii) 0W100pts. of a thermoplastic elastomer and (iii) 0W100pts. of an inorganic filler [the ratio of (ii+iii)/(i) is ≤1.0] with (B) 0.01W0.6pts. of carbon black, is subjected to plasma-treatment and painted. The component B is e.g. furnace black having an average particle diameter of 5W40mμ and the plasma-treatment is carried out e.g. by microwave discharge under an oxygen pressure of 0.1W5Torr.