To provide a sequential groundwater sampler, capable of sequentially sampling groundwater at a particular depth within a groundwater drilled hole, and a sampling method using the same.

A first pipe 10 plays a role as a container for vacuum sample bottle, and is fixedly inserted to a second pipe 20. The second pipe is connected to two cylinders to be moved up and down vertically while surrounding the first pipe by advance and retreat of a second cylinder 50. The second pipe plays a role of passing a syringe needle amounted at the end of a first cylinder piston through a rubber plug of a vacuum sample bottle 80 at the bottom end of the first pipe, or separating the syringe needle from the vacuum sample bottle by advance and retreat of a first cylinder 30. If the second cylinder and the first cylinder sequentially advance, groundwater is injected to the vacuum sample bottle, and if the first cylinder and the second cylinder sequentially retreat, the vacuum sample bottle completed with injection of the sample is separated downward from the first pipe by gravity. The groundwater at the particular depth is sequentially sampled through repeating these processes.