We show that trade enhances skill formation through gains from trade via variety expansion à la Krugman. Although workers are identical as unskilled labour, they differ in productivity as skilled labour. Workers become skilled by incurring training costs. By introducing these settings into a trade model with monopolistic competition, we show that, although trade makes all agents better off, its effect is stronger for skilled than unskilled workers, which stimulates skill acquisition. As a result of less productive workers becoming skilled, the wage dispersion among skilled workers increases.