Abstract: Disclosed herein is a PET-MRI combination apparatus which can extend transaxial and axial fields of view (FOV) by transmitting an output signal from a photo sensor to the outside of an MRI bore using cable. The PET-MRI combination apparatus includes an MRI bore for capturing an MR image of an object. A PET detector is installed inside imaging space of the MRI bore, and is configured such that a plurality of scintillation crystal arrays, each having scintillation crystals arranged in a ring shape, is arranged in a longitudinal direction so as to extend a axial field of view (FOV). A PET circuit unit is installed outside the MRI bore to prevent the PET circuit unit from being influenced by a magnetic field in the MRI bore, and is configured to include a signal amplification circuit and a signal processing circuit. A cable is configured to connect the PET detector to the PET circuit unit.