A multi-cylinder four-stroke engine unit comprising: an engine including a combustion chamber; an intake passage member which is connected to the engine and allows air to be introduced into the combustion chamber; and a throttle valve provided in an intermediate portion of the intake passage member, the combustion chamber, the intake passage member, and the throttle valve being provided for each cylinder, wherein a pressure in a downstream intake passage portion of the intake passage member, that is downstream of the throttle valve, varies in a pressure-variation manner such that: a smaller depression having a smaller difference from atmospheric pressure and a larger depression having a larger difference from atmospheric pressure are created in each four-stroke cycle; and the creation of the smaller and larger depressions is repeated on a four-stroke basis, the engine unit further comprising: a canister connected to a fuel tank and accommodating therein an adsorbent configured to adsorb fuel vapor contained in incoming air from the fuel tank; and a communication passage member configured to establish communication between an inside of the canister and the downstream intake passage portion for each cylinder, the communication passage member having a branched portion for each cylinder, the branched portions respectively connected to the downstream intake passage portions, the engine unit being characterized by comprising: a valve (170, 270) provided to each branched portion of the communication passage member so that a capacity of a part of the communication passage member, the part extending from the intake passage member to the valve, is smaller than a half of a displacement of the engine, wherein an opening degree of the valves (170, 270) being changeable; and a controller (150, 450) configured to control operation of the valves (170, 270) on a basis of the pressure-variation manner in which the creation of the smaller and larger depressions is repeated on the four-stroke basis. an engine including a combustion chamber; an intake passage member which is connected to the engine and allows air to be introduced into the combustion chamber; and a throttle valve provided in an intermediate portion of the intake passage member, the combustion chamber, the intake passage member, and the throttle valve being provided for each cylinder, wherein a pressure in a downstream intake passage portion of the intake passage member, that is downstream of the throttle valve, varies in a pressure-variation manner such that: a smaller depression having a smaller difference from atmospheric pressure and a larger depression having a larger difference from atmospheric pressure are created in each four-stroke cycle; and the creation of the smaller and larger depressions is repeated on a four-stroke basis, the engine unit further comprising: a canister connected to a fuel tank and accommodating therein an adsorbent configured to adsorb fuel vapor contained in incoming air from the fuel tank; and a communication passage member configured to establish communication between an inside of the canister and the downstream intake passage portion for each cylinder, the communication passage member having a branched portion for each cylinder, the branched portions respectively connected to the downstream intake passage portions, a canister connected to a fuel tank and accommodating therein an adsorbent configured to adsorb fuel vapor contained in incoming air from the fuel tank; and a communication passage member configured to establish communication between an inside of the canister and the downstream intake passage portion for each cylinder, the communication passage member having a branched portion for each cylinder, the branched portions respectively connected to the downstream intake passage portions, the engine unit being characterized by comprising: a valve (170, 270) provided to each branched portion of the communication passage member so that a capacity of a part of the communication passage member, the part extending from the intake passage member to the valve, is smaller than a half of a displacement of the engine, wherein an opening degree of the valves (170, 270) being changeable; and a controller (150, 450) configured to control operation of the valves (170, 270) on a basis of the pressure-variation manner in which the creation of the smaller and larger depressions is repeated on the four-stroke basis. a valve (170, 270) provided to each branched portion of the communication passage member so that a capacity of a part of the communication passage member, the part extending from the intake passage member to the valve, is smaller than a half of a displacement of the engine, wherein an opening degree of the valves (170, 270) being changeable; and a controller (150, 450) configured to control operation of the valves (170, 270) on a basis of the pressure-variation manner in which the creation of the smaller and larger depressions is repeated on the four-stroke basis.