Trump, the front-runner to become the Republican candidate in November's election, last week said he would not want to protect NATO members from a future attack by Russia if those countries' contributions to NATO were lagging.
"U.S. election campaigns are very different from Finnish elections, and the rhetoric used is quite a lot stronger... I think at this stage it is best to remain calm and focus on building our NATO membership," Stubb told a press conference.
Finland spends more on defence than the 2% of gross domestic product agreed by NATO member states, Stubb added.
On Sunday Stubb narrowly won Finland's presidential election and will take office on March 1 in charge of security and foreign policy, including the recently approved NATO member's stance towards Russia, with which it shares a long border.
(Reporting by Essi Lehto and Tom Little in Helsinki, editing by Stine Jacobsen, Louise Rasmussen)