An automatic processing device of culture plates (2) for microbiological samples, wherein the processing device (1) includes a support frame (3); a slide (4) provided with a seating (5) configured for removably housing a culture plate (2) and movably mounted on the support frame (3) so as to be selectively displaceable between a first loading position, a plurality of image-acquiring positions, and a first unloading; a camera (6) of a linear type, provided with an optic (7) of a telecentric type and a trilinear sensor, and arranged according to a vertical axis (8) such as to acquire, at an image-acquiring zone, a multiplicity of linear images of corresponding linear portions of an upper surface of the culture plate (2), during the displacing of the slide (4); a first lighting device (11) orientated such as to illuminate the linear portions of an upper surface of the culture plate (2); an advancing device (14) of the slide (4) configured such as to enable obtaining a constant and substantially vibration-free advancing speed of the slide (4) in the image-acquiring zone; and an electronic control device (9) of a functioning of the camera (6), of the lighting device and of the advancing device (14).