A device configured to determine a rotation angle with respect to a proceeding direction includes an accelerometer configured to obtain acceleration information related to movements of the device; a storage unit configured to store the acceleration information; and a controller configured to transform coordinates of the acceleration information, filter the acceleration information on the transformed coordinates, and determine the rotation angle of the device with respect to the proceeding direction of the device by using gravitational acceleration information on the transformed coordinates. The gravitational acceleration information is derived by using information about a time point when a vertical acceleration component at the transformed coordinates of the device has a maximum value, from among the acceleration information.