The invention provides an underground water sampler, which is integrally a strip tubeand comprises a motor section, a vacuum section and a sampling section which are sequentially connected in series and fixed, wherein a linear motor is fixed in the motor section, and the output rod of the linear motor always extends to the sampling section; two ends of the vacuum section are sealed; the whole sampling section is axially communicated, and comprises sampling unit sections which are sequentially connected in series and fixed, a sampling port is formed in each sampling unit section, and a movable valve is arranged inside each sampling port; and each movable valve is fixed on the output rod, a standing valve is fixed on the tube wall upstream each movable valve, and a channel for water flowing is formed in each standing valve. Compared with the prior art, the underground water sampler has the technical effects that a plurality of sampling ports are axially formed in the sampler and can be used for collecting underground water in multiple stratums, so that the collected water samples include water samples of the whole stratum, and the number of underground water can be truly monitored and detected.