Provided is a color camera that captures using environmental light, a monochrome camera that captures using infrared light, a signal processing unit that processes a signal of a color image output from the color camera and a signal of a monochrome image output from the monochrome camera, a storage unit that stores alignment information generated from a color image and a monochrome image captured in a state of sufficient environmental light, an alignment unit that performs an alignment based on alignment information to match positions of a subject shown in a color image and a monochrome image captured in a state of insufficient environmental light, and an image synthesis unit that acquires color information from the aligned color image and performs color conversion to colorize the monochrome image using the color information.