A biological information measurement system that measures physical condition of a test subject on the basis of defecation gas discharged into a bowl of a flush toilet installed in a toilet installation space, the biological information measurement system comprising: a test subject identification device for identifying the test subject who uses the flush toilet; a suction device that sucks gas in the bowl into which the defecation gas is discharged by the test subject; a gas detector provided with a gas sensor that is sensitive to methyl mercaptan gas, as well as to odiferous gas containing a sulfur component other than the methyl mercaptan gas, included in gas sucked by the suction device; a control device that controls the suction device and the gas detector; a storage device that stores first detection data acquired by the gas detector for each of test subjects identified by the subject identification device, wherein the first detection data are related to the methyl mercaptan gas and the odiferous gas; a data analyzer that analyzes physical condition of the test subject on the basis of time-dependent change in a plurality of first detection data items that are detected in defecation acts performed multiple times in a predetermined period, and that is stored in the storage device; and an output device (66, 68, 70) that outputs an analysis result acquired by the data analyzer, wherein the gas detector is configured to sense a healthy-state gas composed of at least one of hydrogen gas, carbon dioxide gas, and methane gas, contained in gas sucked by the suction device, to output second detection data which are related to the healthy-state gas, and wherein the data analyzer acquires a relationship between a first index related to odiferous gas containing a sulfur component, acquired on the basis of first detection data, and a second index related to healthy-state gas, acquired on the basis of second detection data in one defecation act, to analyze physical condition of the test subject on the basis of time-dependent change in the acquired relationship in a defecation act performed multiple times. a test subject identification device for identifying the test subject who uses the flush toilet; a suction device that sucks gas in the bowl into which the defecation gas is discharged by the test subject; a gas detector provided with a gas sensor that is sensitive to methyl mercaptan gas, as well as to odiferous gas containing a sulfur component other than the methyl mercaptan gas, included in gas sucked by the suction device; a control device that controls the suction device and the gas detector; a storage device that stores first detection data acquired by the gas detector for each of test subjects identified by the subject identification device, wherein the first detection data are related to the methyl mercaptan gas and the odiferous gas; a data analyzer that analyzes physical condition of the test subject on the basis of time-dependent change in a plurality of first detection data items that are detected in defecation acts performed multiple times in a predetermined period, and that is stored in the storage device; and an output device (66, 68, 70) that outputs an analysis result acquired by the data analyzer, wherein the gas detector is configured to sense a healthy-state gas composed of at least one of hydrogen gas, carbon dioxide gas, and methane gas, contained in gas sucked by the suction device, to output second detection data which are related to the healthy-state gas, and wherein the data analyzer acquires a relationship between a first index related to odiferous gas containing a sulfur component, acquired on the basis of first detection data, and a second index related to healthy-state gas, acquired on the basis of second detection data in one defecation act, to analyze physical condition of the test subject on the basis of time-dependent change in the acquired relationship in a defecation act performed multiple times.