An electromagnetic and its combined surveying apparatus and method, utilizing small-sized one or three-dimensional magnetic field sensors with high dynamic range and high sensitivity, which can be used together with highly populated receivers for the electromagnetic exploration. The electrical field could be derived from the vertical component of the magnetic field of the highly populated receivers and the magneto-telluric data could be derived by measuring the three components of the magnetic data. Moreover, by means of connecting the same populated receivers with geophones or MEMS accelerometers, and moving the seismic sources together with the mobile electromagnetic source, seismic survey could be carried out. It is therefore able to undertake the interpretation of the seismic, electromagnetic and magneto-telluric data and perform a combined field exploration.