The present invention relates to an analyzing instrument (X1) provided with a capillary (5) for moving a sample liquid. The analyzing instrument (X1) includes a dehumidification region for maintaining a constant moisture content in the capillary (5). Preferably, the dehumidification region has a hygroscopicity of no less than 2%. Preferably, at least part of an inner surface of the capillary (5) extends in the moving direction of the sample liquid and is a water-insoluble high-wettability region having a wettability of no less than 57 mN/m. The dehumidification region and the high-wettability region may be made of Vinylon, for example. Preferably, the analyzing instrument (X1) includes a liquid pooling portion (4) communicating with the capillary (5) and having a portion wider than the capillary (5).