Abstract: A reaction apparatus is provided which is suitable for automatic immunoassay equipment and is capable of conducting treatments in reaction vessels for different reaction conditions such as reaction time and treatment method like a one-step method and a two-step method. The apparatus comprises a conveying mechanism for conveying vessels containing a objective measurement substance around a rotation center. The conveying mechanism comprises a fixed disk 1 for guiding the vessels 5 along a spiral lane 2, and a rotation disk 3 for guiding the vessels 5 along radial lanes. The vessels 5 are inserted at intersection points of the spiral lane and the radial lanes, and are conveyed with the rotation of the radial lanes along the spiral lane. The mechanism is constituted such that the vessels 5 for long-time treatment and the vessels for short-time treatment are inserted to the same insertion position and the vessels 5 for short-time treatment is taken out from an intermediate way of the conveying route.