[en] In this research, a radiation detector based on a silicon photomultiplier (SiPM) and Ce doped Gd₃Al₂Ga₃O₁₂(GAGG(Ce)) scintillator was developed for nuclide analysis, and the spectroscopic characteristics were compared with those of an optical-fiber-based radiation detector. The results showed that the developed detector was 1.64–3.86 times more efficient for detection compared to the optical-fiber-based detector, and the R-squared value of the linearity of the developed detector was 0.99760 according to the radiation intensity, demonstrating the best linearity. The optical-fiber-based detector had a poor resolution characteristic with respect to the gamma-ray emission energy, whereas the developed SiPM-based detector had a high resolution of 17.2% at 122 keV (the gamma-ray emission energy of ⁵⁷Co), 13.5% at 356 keV (the gamma-ray emission energy of ¹³³Ba), 6.9% at 511 keV (the gamma-ray emission energy of ²²Na), and 5.8% at 662 keV (the gamma-ray emission energy of ¹³⁷Cs). Furthermore, it was confirmed that the R-squared value in the gamma-ray energy range of 122–662 keV was 0.99860, indicating good linearity. Therefore, the PMT-based radiation detectors used in narrow environments subject to electromagnetic fields can be replaced with the SiPM-based radiation detector by applying the results of this study to miniaturized signal processors.