Provided is a laminar-scavenging two-cycle engine, which can have a higher laminar-scavenging effect than that of the laminar-scavenging two-cycle engine of the prior art and which can expect drastically excellent effects on the stabilization of combustion and on the blow-by prevention. The laminar-scavenging two-cycle engine is characterized in that a scavenging passage (4) is constituted to include a portion (or a crankcase side portion (4a)) extending along a crankcase (9) and a portion (or a cylinder side portion (4b)) extending along a cylinder (10) and to have a length larger than the sum of the diameter and stroke of the cylinder (10), in that an ambient air introducing passage (11) for introducing the leading air into the scavenging passage (4) is connected to an intermediate portion of the scavenging passage (4), and in that a notch (8a) for opening a scavenging port (7) to the side of the crankcase (9) when a piston (8) is near the top dead center is formed in the piston (8).