Immunochromatographic device

An immunochromatographic device for detecting a detection target in an analyte which comprises a sample droplet-receiving member, a labeling substance-holding member having a labeling substance-containing part, a chromatography medium member having a detection part and an absorption member and which contains a nitrous acid compound and an organic acid or an organic acid derivative,

• wherein the sample droplet-receiving member, the labeling substance-holding member, the chromatography medium member and the absorption member are arranged in a manner that a sample develops in this order,
• the immunochromatographic device has a part containing the nitrous acid compound and a part containing the organic acid or the organic acid derivative at upstream positions from the labeling substance-containing part, and
• the part containing the nitrous acid compound and the part containing the organic acid or the organic acid derivative are not substantially in contact with each other in the thickness direction
• wherein the organic acid or the organic acid derivative is a nitrogen-containing heterocyclic compound represented by the following formula (1),
• wherein in the formula (1), R1 and R2 each independently represents a hydrogen atom, a carbonyl group or an alkyl group which may have a substituent, wherein alkyl groups may bind to each other to form a ring and form an alicyclic hydrocarbon ring or an aromatic hydrocarbon ring,
• A represents a single bond or a double bond, X represents —C(═O)— or —(CH2)n—, Y represents a carbon atom or a nitrogen atom, n is 1 or 2, and
• Z represents a hydrogen atom, a hydroxyl group, an alkyl group which may have a substituent, —C(═O)R3 or —O—C(═O)R3, wherein R3 represents an alkyl group which may have a substituent or an alkoxy group.