According to one embodiment, an ultrasonic diagnostic apparatus sets a desired period with reference to a predetermined time phase in each heartbeat of the object, sequentially executes ultrasonic scanning on a plurality of sub-volumes in a period including the diagnosis period to acquire sub-volume data corresponding to a plurality of time phases, controls acquisition timing of the sub-volume data from a time point elapsed from the predetermined time phase by a predetermined period of time while switching the sub-volume, generates composite sub-volume data or a full volume data constituted by a plurality of sub-volume data by performing combining processing of the sub-volume data acquired in the different diagnosis periods, detects at least one of a cyclic change of a heartbeat signal and a change in the number of sub-volume data acquired in the one diagnosis period and performs combining processing of sub-volume data based on a detection result.
