The design and operating principle of a laser interferometric mercury manometer functioning as a component of State Primary Standard GET 101- 2011 of the unit of pressure for the region of absolute pressure in the range 1 center dot 10(-1)-7 center dot 10(5) Pa are described. The manometer utilizes a cats'-eye type floating device that dampens the surface waves of the mercury in combination with special protective rings that stabilize the contrast of the interference pattern.