A biochemical assay device, comprising: - a reaction cassette for biochemical assay, comprising: a first space configured to accommodate liquid, having a first opening, a direction of the first opening being directed upward; a second space having a second opening, a direction of the second opening being perpendicular to the direction of the first opening, wherein the first space and the second space are disposed such that when the reaction cassette is rotated allowing the liquid to drain into the second space; a third space located below the first space and having a third opening, a direction of the third opening being upward such that when the reaction cassette is reversibly rotated allowing the liquid to drain into the third space; and a first inner partition wall, connected with the second opening and the third opening, acting as a liquid flow channel between the second space and the third space; and - a sampling part configured to be coupled to the reaction cassette, comprising: a sampling tube configured to draw a liquid sample; an absorption compartment containing an absorption material inside thereof; and a reservoir which is configured to store a liquid reagent and which is sealed with an aluminum foil, wherein the aluminum foil is removed during insertion of the sampling part into the reaction cassette; characterized in that said first space has rounded edges, an array of bumps is disposed in the third space to create turbulence of the liquid, and a bump is disposed on a transverse beam beside the sampling tube, which bump acts as a barb to peel off the aluminum foil while the sampling part and the reaction cassette are assembled. - a reaction cassette for biochemical assay, comprising: a first space configured to accommodate liquid, having a first opening, a direction of the first opening being directed upward; a second space having a second opening, a direction of the second opening being perpendicular to the direction of the first opening, wherein the first space and the second space are disposed such that when the reaction cassette is rotated allowing the liquid to drain into the second space; a third space located below the first space and having a third opening, a direction of the third opening being upward such that when the reaction cassette is reversibly rotated allowing the liquid to drain into the third space; and a first inner partition wall, connected with the second opening and the third opening, acting as a liquid flow channel between the second space and the third space; and a first space configured to accommodate liquid, having a first opening, a direction of the first opening being directed upward; a second space having a second opening, a direction of the second opening being perpendicular to the direction of the first opening, wherein the first space and the second space are disposed such that when the reaction cassette is rotated allowing the liquid to drain into the second space; a third space located below the first space and having a third opening, a direction of the third opening being upward such that when the reaction cassette is reversibly rotated allowing the liquid to drain into the third space; and a first inner partition wall, connected with the second opening and the third opening, acting as a liquid flow channel between the second space and the third space; and - a sampling part configured to be coupled to the reaction cassette, comprising: a sampling tube configured to draw a liquid sample; an absorption compartment containing an absorption material inside thereof; and a reservoir which is configured to store a liquid reagent and which is sealed with an aluminum foil, wherein the aluminum foil is removed during insertion of the sampling part into the reaction cassette; a sampling tube configured to draw a liquid sample; an absorption compartment containing an absorption material inside thereof; and a reservoir which is configured to store a liquid reagent and which is sealed with an aluminum foil, wherein the aluminum foil is removed during insertion of the sampling part into the reaction cassette;