A trajectory estimation apparatus, method, and medium using a triaxial accelerometer are provided. The trajectory estimation apparatus includes a motion sensing module which measures an acceleration component for each of three axes from the input 3D gesture using a triaxial accelerometer, a gravitational component removal module which calculates a gravitational acceleration component and removes the gravitational acceleration component from the acceleration component, a gesture determination module which identifies gesture type represented by an acceleration component obtained as the result of the removal performed by the gravitational component removal module, and a compensation module which compensates for the acceleration component obtained as the result of the removal performed by the gravitational component removal module by using different compensation methods for different gesture types.