Provided is an apparatus for monitoring a malfunctioning state of a global positioning system (GPS) satellite, the apparatus comprising: an orbit computing unit to compute an orbit of a geostationary satellite; a data receiver to receive GPS data from the GPS satellite; a data correction unit to correct an error in a clock error value of the GPS data; a first computing unit to compute a data pseudorange between the GPS satellite and a base station based on the corrected GPS data; a second computing unit to compute a geographical distance between the GPS satellite and the base station; and a determining unit to determine a malfunctioning state of the GPS satellite by comparing the data pseudorange and the geographical distance.