An aqueous gel that is prepared by gelling a polymer components, the polymer components containing polymer A, which is obtained by polymerizing a monomer component containing a betaine monomer represented by the formula (I): wherein R1 represents hydrogen atom or an alkyl group, R2 represents an alkylene, arylene, aralkylene, —COOH— or —CONH— group; R3 and R4 represent an alkyl group, and R5 represents an alkylene group, and a polymer B, which is obtained by polymerizing a monomer component containing an acidic monomer represented by the formula (II): wherein R1 represents hydrogen atom or an alkyl group; R6 represents an optionally neutralized sulfonate group, an optionally neutralized phosphate group, or an alkyl, aryl, aralkyl, carboxyl or amino group carrying an optionally neutralized sulfonate group or an optionally neutralized phosphate group.