Provided are a two-dimensional array antenna and a device for detecting an internal object using the same. The device includes a plurality of unit antennas in a two-dimensional array of m columns and n rows on a board (where m and n are integers greater than 1), a first switch selecting one or more transmitting antenna to radiate a pulse signal onto an internal object in a structure from among the unit antennas; a second switch selecting one or more receiving antenna to collect a signal reflected from the internal object from among the unit antennas, and a transceiving analysis module analyzing information about the position and shape of the internal object.