In a proximity X-ray exposure apparatus using a point source as a light source, a laser beam (21) is focused on a circular disk-like target (14) arranged in an X-ray source unit to irradiate it, thus generating a plasma and then X-rays (17). The circular disk-like target (14) has four types of quadrant first-, second-, third-, and fourth-wavelength light-emitting portions (14a, 14b, 14c, 14d) which are made of different materials and divided equiangularly in the radial direction. The target (14) is rotatably controlled by a rotational drive mechanism in synchronism with pulse emission. As the rotational angle of the target (14) is controlled in synchronism with emission of the laser beam (21), the material (type) of the target (14) can be selected from the first-, second-, third-, and fourth-wavelength light-emitting portions (14a, 14b, 14c, 14d).