The present invention provides a photoacoustic signal-processing device, a photoacoustic signal-processing system, and photoacoustic signal-processing, which, when ascertaining the position of an inserted object that is inserted in a subject being examined using photoacoustic images, are able to display the inserted object depicted on the photoacoustic images so as to allow determination of whether or not the inserted object is directly below the probe. Among multiple photoacoustic images resulting from photoacoustic detection signals detected in multiple orientations during peak-searching mode, a peak-specifying means (31) specifies the photoacoustic image for which the photoacoustic detection signal is strongest on the basis of said multiple photoacoustic images. An orientation-determining means (32) determines whether or not the orientation of the probe (11) when detecting the photoacoustic waves of the photoacoustic image-generating source during normal mode coincides with the orientation of the probe (11) when detecting photoacoustic waves of the generating source for the photoacoustic image specified by the peak-specifying means. A display control means (27) causes photoacoustic images to be displayed on a display screen, and, when the orientation-determining means (32) determines that the orientations coincide, causes a message to that effect to be displayed on the display screen.