A leakage detection device detects leakage in a PCV passage that at least includes a scavenging line that communicates between a crank chamber of an engine and a portion of an intake passage of the engine that is on a downstream side of a throttle valve and a fresh air line that communicates between the crank chamber and a portion of the intake passage that is on an upstream side of the throttle valve. The leakage detection device includes a pressure measurement, a first valve and a leakage determination unit. The pressure measurement unit measures pressure in the PCV passage. The first valve opens/closes the fresh air line. The leakage determination unit determines presence or absence of leakage in the PCV passage on a basis of the pressure in the PCV passage at a time when the first valve is closed.