An x-ray topography apparatus in which x-rays diffracted from a sample which is scanned with a linear x-ray are detected by an x-ray detector to obtain a planar diffraction image. In this x-ray topography apparatus, the x-ray detector is an imaging plate shaped as a cylinder and provided with a surface area that is larger than the sample, and the imaging plate is made to undergo α-rotation about the center axis of the cylindrical shape in coordination with scanning movement of the linear x-rays. The center axis of the cylindrical shape extends in a direction at a right angle with respect to the direction of the scanning movement of the linear x-rays.