Abstract: A blender having bi-directionally rotatable blades includes: a blade assembly including a main blade shaft that is provided to allow a first blade and a first main coupler to integrally rotate in a forward direction and a reverse-rotation blade shaft that is provided to allow a second blade and a first reverse-rotation coupler to integrally rotate in a reverse direction; and a gearbox assembly including a main gear shaft that is provided to allow a second main coupler and a main gear to rotate in the forward direction, at least one sub-gear that is engaged with the main gear and rotates in the reverse direction, a ring gear to which the sub-gear is internal and engaged, and a second reverse-rotation coupler that is configured to integrally rotate with the ring gear in the reverse direction and transmit the reverse rotation to the first reverse-rotation coupler.