A reaction cassette for biochemical assay, the reaction cassette being configured to receive a sampling part for storing a sample along with a liquid reagent, the sampling part being configured to be inserted to the reaction cassette from above, wherein the reaction cassette comprises a housing with structural walls defining a liquid mixing space for accommodating a first mixing zone, a second mixing zone, and a third mixing zone, an optical detection zone, and an absorption zone, and wherein the liquid mixing space comprises: the first mixing zone configured to accommodate a liquid, having rounded edges and corners, and including a first opening which faces upward such that the sample along with the liquid reagent can flow from the sampling part into the first mixing zone upon inserting the sampling part into the reaction cassette when the reaction cassette is in an upright position; the optical detection zone having the capability of receiving a mixture of liquid and reagent, the optical detection zone being disposed such that the liquid mixture flows from the first mixing zone into the optical detection zone when the reaction cassette is rotated clockwise by 90° from its upright position; the second mixing zone having the capability of receiving a mixture of liquid and reagent, the second mixing zone being disposed below the first mixing zone such that the liquid mixture flows from the optical detection zone into the second mixing zone via the first inclined plane when the reaction cassette is rotated counterclockwise by 90° back to its upright position, and such that the liquid mixture is caused to flow back into the optical detection zone when the reaction cassette is rotated clockwise by 90° from its upright position; the third mixing zone having the capability of receiving a mixture of liquid and reagent, the third mixing zone being disposed such that that the liquid mixture flows from the optical detection zone into the third mixing zone via a second inclined plane disposed between the second and the third mixing zones when the reaction cassette is rotated counterclockwise equal to 175° from its previous position; the absorption zone having the capability of receiving a mixture of liquid and reagent, the absorption zone being disposed above the third mixing zone and having a spill-proof wall disposed between the third mixing zone and the absorption zone to prevent the liquid mixture in the third mixing zone from overflowing into the absorption zone by accident, and the absorption zone being disposed such that when the reaction cassette is rotated counterclockwise by 90° from its upright position, the liquid mixture is caused to flow to the absorption zone to be absorbed by absorbent material included in the absorption zone; and wherein at least one of the first mixing zone, the second mixing zone, and the third mixing zone comprises at least one blending structure for generating a vortex phenomenon in liquid, thereby improving the degree of mixture of a liquid sample and a dried reagent. the first mixing zone configured to accommodate a liquid, having rounded edges and corners, and including a first opening which faces upward such that the sample along with the liquid reagent can flow from the sampling part into the first mixing zone upon inserting the sampling part into the reaction cassette when the reaction cassette is in an upright position; the optical detection zone having the capability of receiving a mixture of liquid and reagent, the optical detection zone being disposed such that the liquid mixture flows from the first mixing zone into the optical detection zone when the reaction cassette is rotated clockwise by 90° from its upright position; the second mixing zone having the capability of receiving a mixture of liquid and reagent, the second mixing zone being disposed below the first mixing zone such that the liquid mixture flows from the optical detection zone into the second mixing zone via the first inclined plane when the reaction cassette is rotated counterclockwise by 90° back to its upright position, and such that the liquid mixture is caused to flow back into the optical detection zone when the reaction cassette is rotated clockwise by 90° from its upright position; the third mixing zone having the capability of receiving a mixture of liquid and reagent, the third mixing zone being disposed such that that the liquid mixture flows from the optical detection zone into the third mixing zone via a second inclined plane disposed between the second and the third mixing zones when the reaction cassette is rotated counterclockwise equal to 175° from its previous position; the absorption zone having the capability of receiving a mixture of liquid and reagent, the absorption zone being disposed above the third mixing zone and having a spill-proof wall disposed between the third mixing zone and the absorption zone to prevent the liquid mixture in the third mixing zone from overflowing into the absorption zone by accident, and the absorption zone being disposed such that when the reaction cassette is rotated counterclockwise by 90° from its upright position, the liquid mixture is caused to flow to the absorption zone to be absorbed by absorbent material included in the absorption zone; and wherein at least one of the first mixing zone, the second mixing zone, and the third mixing zone comprises at least one blending structure for generating a vortex phenomenon in liquid, thereby improving the degree of mixture of a liquid sample and a dried reagent.