We demonstrate a photoelectrical readout of negatively charged nitrogen-vacancy (NV−) centers by utilizing a lateral diamond p–i–n diode structure. We found that the photocarriers generated at NV centers are efficiently extracted in the depletion layer even at zero voltage. The transport mechanism for photoexcited minority carriers was investigated by varying the nitrogen ion implantation dose. The minority carrier diffusion length decreased when the photocarriers passed through the implantation region, particularly at a high nitrogen ion dose. From photoelectrically detected magnetic resonance (PDMR) measurements, the photocurrent was found to exhibit a minimum at approximately 2.87 GHz upon microwave irradiation with a contrast of 12%, while this dip was observed to split upon the application of a static magnetic field. The PDMR signal was found to depend on the measurement position. This study paves the way for efficient electrical detection for quantum sensors based on device technologies.