Hair-treatment composition and hair-treatment method using same

Provided is a hair-treatment composition containing: a first amphoteric surfactant having a structure represented by general formula (1) below; at least one type of second amphoteric surfactant selected from the group consisting of fatty acid amide propyldimethylaminoacetic acid betaines, alkyldimethylaminoacetic acid betaines, N-acylaminoethyl-N-2-hydroxyethylaminocarboxylic acid salts and N-acylaminoethyl-N-carboxymethoxyethylaminocarboxylic acid salts fatty acid amide propyldimethylaminoacetic acid betaines, alkyldimethylaminoacetic acid betaines; and an acidic amino acid. In general formula (1), R1 represents an alkyl group the carbon number of which is 6 to 20; R2 represents a methyl group, an ethyl group, or a hydroxyethyl group; R3 represents a methyl group, an ethyl group, or a -CH2COOH group; and n is an integer from 1 to 3.