A drawing surface adjusting mechanism for use with a scanning pattern drawing apparatus capable of not only moving a drawing board in a vertical direction but also tilting it, whereby the chance of bringing the drawing surface within the depth of focus of a scanning lens is increased even if the drawing surface has waviness or other flaws within the width of a single storke of scanning. The drawing surface adjusting mechanism of the invention includes a drawing board for supporting a workpiece that is to be scanned with a scanning optical system by means of a unidirectionally tracing light beam, transport means for allowing the drawing board and the scanning optical system to slide relative to each other in a direction that crosses the direction of beam tracing at right angles, a first and a second drive mechanism which are spaced apart in the tracing direction and which move one side of the drawing board in a direction parallel to the direction of the beam, tilt control means for inclining the drawing board with respect to the transport means by making the drive amount of the first drive means different from that of the second drive means, and translation control means for effecting a translational movement of the drawing board with respect to the transport means by making the drive amount of the first drive means equal to that of the second drive means.