Fixed-depth soil gas and underground water sampling integrated device

The utility model provides a fixed-depth soil gas and underground water sampling integrated device which comprises a sampling well and a sampling head. The sampling well comprises a slotted pipe and asedimentation pipe. The sampling head comprises an upper sealing cover and a lower sealing cover and is tightly connected with the inner wall of the slotted pipe to form a sampling space; a lower drainage pipeline, an upper drainage pipeline, a sampling pipeline and a sampling rod are arranged downwards from a well mouth of the sampling well, the lower drainage pipeline penetrates through the upper sealing cover and the lower sealing cover in a sealed mode, and a drainage port is formed in the position, close to the top side of the upper sealing cover, of the upper drainage pipeline. A sampling opening is formed in the position, close to the top side of the lower sealing cover, of the sampling pipeline after the sampling pipeline penetrates through the upper sealing cover; the vacuum pumpis selectively communicat