A flow cell comprising: a flow path in which a specimen fluid and a sheath fluid flow in use; a specimen flow path arranged to introduce the specimen fluid into the flow path, provided on a central flow line of the flow path; a first sheath flow path and a second sheath flow path arranged to introduce the sheath fluid into the flow path; and a merging portion at which the specimen flow path, the first sheath flow path and the second sheath flow path merge together, the merging portion consisting of a first side surface, a second side surface, the first and second side surfaces (26B, 26C) facing each other, the distance between the first and second side surfaces (26B, 26C) defining the width of the merging portion, an upper surface arranged between the first and second side surfaces (26B, 26C), a lower surface arranged between the first and second side surfaces (26B, 26C), the lower and upper surfaces (26E, 26D) facing each other, the distance between the lower and upper surfaces (26E, 26D) defining the height of the merging portion, and an end surface; the first sheath flow path having a first introducing opening formed in the first side surface, and being adjacent to the upper surface; the second sheath flow path having a second introducing opening formed in the second side surface, and being adjacent to the lower surface; the first introducing opening and the second introducing opening facing the central flow line of the flow path when viewed along a height direction of the merging portion and being disposed at positions that are offset in the height direction of the flow path; the flow cell being characterised in that the end surface is adjacent to the first side surface, second side surface, upper surface and lower surface, and in that the specimen flow path has a specimen introducing opening, formed at the end surface at an intermediate portion in both the height and width directions, so that the specimen introducing opening is located at a non-zero distance from the first side surface, the second side surface, the upper surface and the lower surface. a flow path in which a specimen fluid and a sheath fluid flow in use; a specimen flow path arranged to introduce the specimen fluid into the flow path, provided on a central flow line of the flow path; a first sheath flow path and a second sheath flow path arranged to introduce the sheath fluid into the flow path; and a merging portion at which the specimen flow path, the first sheath flow path and the second sheath flow path merge together, the merging portion consisting of a first side surface, a second side surface, the first and second side surfaces (26B, 26C) facing each other, the distance between the first and second side surfaces (26B, 26C) defining the width of the merging portion, an upper surface arranged between the first and second side surfaces (26B, 26C), a lower surface arranged between the first and second side surfaces (26B, 26C), the lower and upper surfaces (26E, 26D) facing each other, the distance between the lower and upper surfaces (26E, 26D) defining the height of the merging portion, and an end surface; the first sheath flow path having a first introducing opening formed in the first side surface, and being adjacent to the upper surface; the second sheath flow path having a second introducing opening formed in the second side surface, and being adjacent to the lower surface; the first introducing opening and the second introducing opening facing the central flow line of the flow path when viewed along a height direction of the merging portion and being disposed at positions that are offset in the height direction of the flow path; the flow cell being characterised in that the end surface is adjacent to the first side surface, second side surface, upper surface and lower surface, and in that the specimen flow path has a specimen introducing opening, formed at the end surface at an intermediate portion in both the height and width directions, so that the specimen introducing opening is located at a non-zero distance from the first side surface, the second side surface, the upper surface and the lower surface.