An imaging apparatus of the present invention includes an acceleration detecting unit for detecting a vector of a first direction based on an output signal from a three-axis acceleration sensor, an angle obtaining unit for obtaining a relative rotation angle around a roll axis among a plurality of frame images sequentially captured, and a direction estimating unit for estimating a direction of gravity different from the first direction based on the obtained relative rotation angle around the roll axis and the detected vector of the first direction. Thus, it is possible to estimate a posture of the apparatus more properly.