To reduce an offset caused by the atmospheric pressure fluctuation of a height sensor for detecting master disk height in an electron beam master disk exposure device.

This master disk exposure device is constituted of a vacuum chamber 12 housing a rotary stage 15 rotated with a master disk 14 placed thereon and a linearly moved stage 16 for driving the master disk 14 in a radial direction; an electron beam lens barrel 11 fixed to the upper wall 12a of the vacuum chamber 12 to irradiate the surface of the original disk 14 with an electron beam 13, a projection part 18a for obliquely projecting light rays 19 through a first transparent window W1 formed on the upper wall 12a toward the vicinity of the electron beam irradiation spot of the master disk 14, and a light receiving part 18b for receiving light rays 20 reflected on the surface of the master disk 14 through a second transparent window W2 formed on the upper wall 12a. The exposure device is further provided with a height sensor 18 for detecting the surface height of the master disk 14 on the basis of a light receiving position of a light receiving position sensor disposed in the light receiving part 18b. The light projection part 18a and the light receiving part 18b are fixed to the electron beam lens barrel 11 through a height sensor fixing member 31.