The invention relates to a position detection device, a processing apparatus, and a program, for example, a novel device detecting the postion of an object more successfully based on image data. A position detection device according to an embodiment includes a pitch acquisition unit and a position detection unit. The pitch acquisition unit acquires a pitch at which target objects are arranged, based on a spectral analysis performed on captured image data of the target objects. The position detection unit detects positions of the target objects based on the pitch.