J-PARC 3-GeV Rapid Cycling Synchrotron (RCS) has two functions: as a proton beam driver to the spallation neutron source at the Material and Life Science Facility (MLF) and also as an injector to the Main Ring (MR). However the required beam parameters for each facility are different. The pulse steering magnet (PSTR) was developed to satisfy these requirements by switching the painting area in each acceleration cycle of MLF and MR and to realize center injection at 400 MeV. Therefore there are two operation modes, painting injection and center injection, for operation of PSTR. Painting injection switches beam size (emittance) between MR and MLF and center injection sets injected beam in the same phase space position. The former is operated with pulse mode of trapezoid current pattern and the latter is realized in DC mode. The magnet field measurement was also performed with two operation modes. In this paper we will report the result of the field measurement of PSTR.