A cartridge for detecting a target substance which is rotated around a rotating shaft, comprising: a chamber for accommodating a sample containing the target substance; wherein the chamber comprises: a first region in which the sample is accommodated; a second region disposed at a position closer to the rotating shaft than the first region; two protrusions protruding inside the chamber from a position between the first region and the second region, and provided at positions facing each other in a circumferential direction of a circle centered on the rotating shaft, wherein each protrusion has a tip portion and a tip; the cartridge being characterised in that a distance of a first width, which is the largest width in the circumferential direction of the first region, is designated distance D1, and a straight line bisecting the first width in the radial direction of the rotating shaft is designated straight line A, and a distance of a second width, which is a width in the circumferential direction between the straight line A and the tip is designated distance D2, and the distance corresponding to half of the first width is designated distance D3, wherein the distance D2 is in the range of 40% to 98% of the distance D3. a chamber for accommodating a sample containing the target substance; wherein the chamber comprises: a first region in which the sample is accommodated; a second region disposed at a position closer to the rotating shaft than the first region; two protrusions protruding inside the chamber from a position between the first region and the second region, and provided at positions facing each other in a circumferential direction of a circle centered on the rotating shaft, wherein each protrusion has a tip portion and a tip; the cartridge being characterised in that a distance of a first width, which is the largest width in the circumferential direction of the first region, is designated distance D1, and a straight line bisecting the first width in the radial direction of the rotating shaft is designated straight line A, and a distance of a second width, which is a width in the circumferential direction between the straight line A and the tip is designated distance D2, and the distance corresponding to half of the first width is designated distance D3, wherein the distance D2 is in the range of 40% to 98% of the distance D3. a first region in which the sample is accommodated; a second region disposed at a position closer to the rotating shaft than the first region; two protrusions protruding inside the chamber from a position between the first region and the second region, and provided at positions facing each other in a circumferential direction of a circle centered on the rotating shaft, wherein each protrusion has a tip portion and a tip; the cartridge being characterised in that a distance of a first width, which is the largest width in the circumferential direction of the first region, is designated distance D1, and a straight line bisecting the first width in the radial direction of the rotating shaft is designated straight line A, and a distance of a second width, which is a width in the circumferential direction between the straight line A and the tip is designated distance D2, and the distance corresponding to half of the first width is designated distance D3, wherein the distance D2 is in the range of 40% to 98% of the distance D3.