An apparatus and a method for searching a transmission signal from a neighboring base station acquires a location of present cell through initial cell searching, sets an operation mode according to whether or not rough location information of neighboring cell is provided by the present cell, sets a mask window based on time information of the cell which is already known, searches the section of mask window and remaining sections selectively according to the operation mode, and acquires precise time information of neighboring cells using energy peak searched from the selected section. In this manner the neighboring cells can be searched rapidly and easily by adding the window masking function to the initial cell searching apparatus.