In the field of biomagnetic measurements, optically pumped atomic magnetometers (OPAMs) are expected to be alternative sensors to magnetometers based on superconducting quantum interference devices (SQUIDs). In addition, miniaturized OPAMs are required for practical use. To address this issue, we developed a compact module of a high-sensitivity OPAM with a pump probe arrangement and potassium used as the sensing atom. Because the noise spectrum density of the OPAM reached 21 f T-rms/Hz(1/2) at 10 Hz, we attempted to use it to measure human magnetocardiograms (MEGs). Compared with the results obtained with SQUID-based magnetometers, we could successfully observe distinct features of event-related desynchronization in the 8-13 Hz band associated with eye opening. The results demonstrate the feasibility of using the OPAM module for neuromagnetic field measurements. (C) 2015 The Japan Society of Applied Physics