A sampling method includes a sampling step and a cleaning step. The sampling step includes a first sample introduction step of introducing a first sample from a first cell culturing device to a more downstream side than a first connection portion in a sampling flow path, a first returning step of causing the first sample in the sampling flow path to flow into an introduction path from the first connection portion after the first sample introduction step, and a first flowing step of bringing the first sample into contact with a second sensor after the first returning step.