In an interview on CNBC's "Squawk Box," the Alaska Republican and former Marine questioned where the strategy is to prevent the U.S. from being a "cyber punching bag."
Sullivan, a member of the committee that's chaired by Sen. John McCain, said the hearing is aimed at finding out the extent of hacking by Russia, China and other foreign actors.
But the senator said he has seen no credible evidence that Russia was motivated to use cyberattacks to swing the presidential election.
"From my perspective, it's clear Donald Trump [and] Mike Pence won the election fair and square," Sullivan said. "Those who are using the Russian hacking issue to somehow delegitimatize the election results ... are simply wrong and doing a disservice to Americans."
President Barack Obama, who requested a report on Russian hacking, is expected on Thursday to be briefed on the findings.
Trump is set to meet with U.S. intelligence officials on Friday in New York.