To largely improve detection efficiency.

In an image detecting device obtaining an image signal related to a scanned object by scanning a beam or a probe in accordance with a scan signal relating to the scanned object, as the scan signal, the horizontal/vertical scan signals X (t) and Y (t) of arcsine-shaped pulse as follows is repeatedly used respectively as 1 cycle. [1 cycle of horizontal scan signal] 0≤t≤a, X (t)=(A/π) {π/2+arcsin (2t/a-1}. [1 cycle of vertical scan signal] 0≤t≤b, Y (t)=(B/π) {π/2+arcsin (2t/b-1}. where, A, B represent scan widths, a, b the periods (a<b), and t the time in 1 cycle.