Present invention proposes an apparatus and method for deciding entrance and exit of moving objects using two or more transmission units and only one reception unit which are installed on a gateway of a space to be measured. The two or more transmission units comprises a first transmission unit installed on one side surface of a gateway of a space to be measured to emit a first pulse in a first period; a second transmission unit installed in an inside direction of the space on the installation surface of the first transmission unit to emit a second pulse which has the first period and a phase that is different from a phase of the first pulse.