The 20-year-old, who rides for the Visma-Lease a Bike cycling team, outsprinted countryman Ben Turner and Italy's Andrea Bagioli to win the 206.1 km stage from the southern city of Katowice to the Tatra mountain resort of Zakopane.
Frenchman Paul Lapeira held on to the yellow jersey, maintaining his overall lead in the general classification.
Poland’s top finisher, Rafał Majka, crossed the line in 23rd place.
There were no major changes in the overall standings, Polish state news agency PAP reported.
Lapeira leads Monaco’s Victor Langellotti by eight seconds, with Switzerland’s Jan Christen 12 seconds back.
Poland’s Majka, the 2014 Tour de Pologne champion, sits in eighth, 14 seconds off the lead.
Majka is racing in what he has said are the final weeks of his professional career.
The seven-leg race continues on Saturday with a key mountainous stage starting and ending in the resort of Bukowina Tatrzańska.
(gs)
Source: IAR, PAP