1. An imaging apparatus comprising: an imaging device; and a signal processing unit for analyzing an output signal from the imaging device and detecting a defective pixel included in the imaging device, wherein the imaging device inputs the same subject light on a local area basis including a plurality of pixels of the imaging device, acquires an image signal lower than a pixel resolving power corresponding to the pixel density of the imaging device, and outputs the image signal to the signal processing unit, and the signal processing unit compares pixel values of the same color pixels included in the local area on a local area basis including a cluster of the plurality of pixels of the imaging device, and detects a defective pixel based on the comparison result; wherein the signal processing unit executes a process of determining a pixel of interest to be a defective pixel when a standard deviation of pixel values of the same color pixels included in the local area is larger than a preset threshold value (TH1), and when a difference absolute value between an average of intermediate pixel values except maximum and minimum pixel values of the same color pixels included in the local area, and a pixel value of the pixel of interest is larger than a preset threshold value (TH2).