An outboard motor comprising: a propeller shaft; an engine including at least one cylinder in which a piston is provided configured to reciprocate, and a crankshaft extending in a horizontal direction perpendicular to a direction in which the propeller shaft extends, the crankshaft is configured to receive reciprocating movement of the piston to generate a rotational motion of the crankshaft; a further shaft disposed in a direction that intersects with a direction in which the cylinder extends and in a downward direction with respect to the crankshaft, the further shaft extends parallel to a direction in which the crankshaft extends, the further shaft is configured to be driven by the crankshaft; a first gear provided on the further shaft; a second gear configured to be driven in decelerated manner by the first gear; a third gear mounted on the crankshaft, the third gear meshes with a fourth gear mounted on the further shaft; a drive shaft that is connected to the second gear and extends in an upward-downward direction; and a propeller connected to the propeller shaft configured to be rotated by the drive shaft, characterized in that said further shaft is a balance shaft, the third gear and the fourth gear include the same number of teeth and mesh with each other at a substantially constant speed, wherein the driving of the first gear is decelerated and transmitted to the second gear, wherein the first gear is disposed substantially at a center of the balance shaft in a direction in which the balance shaft extends, and the drive shaft is disposed substantially at a center of the balance shaft in the direction in which the balance shaft extends. a propeller shaft; an engine including at least one cylinder in which a piston is provided configured to reciprocate, and a crankshaft extending in a horizontal direction perpendicular to a direction in which the propeller shaft extends, the crankshaft is configured to receive reciprocating movement of the piston to generate a rotational motion of the crankshaft; a further shaft disposed in a direction that intersects with a direction in which the cylinder extends and in a downward direction with respect to the crankshaft, the further shaft extends parallel to a direction in which the crankshaft extends, the further shaft is configured to be driven by the crankshaft; a first gear provided on the further shaft; a second gear configured to be driven in decelerated manner by the first gear; a third gear mounted on the crankshaft, the third gear meshes with a fourth gear mounted on the further shaft; a drive shaft that is connected to the second gear and extends in an upward-downward direction; and a propeller connected to the propeller shaft configured to be rotated by the drive shaft, characterized in that said further shaft is a balance shaft, the third gear and the fourth gear include the same number of teeth and mesh with each other at a substantially constant speed, wherein the driving of the first gear is decelerated and transmitted to the second gear, wherein the first gear is disposed substantially at a center of the balance shaft in a direction in which the balance shaft extends, and the drive shaft is disposed substantially at a center of the balance shaft in the direction in which the balance shaft extends.