A first stage rainfall sampler, which is capable of automatically sampling rainfall step by step without requiring a motive power.A plurality of sampling containers are swingably and detachably hung down from the circumference of a tumbler which is supported so as to revolve within a vertical plane, at intervals so as to correspond to an outlet port of a funnel in turn. The tumbler is provided with a weight for variably forming a balanced condition between it and rainfall contained by the sampling containers.