A lightray treatment device (1) for hardening fingernail modeling compounds has a lightray treatment chamber (3) enclosed in a housing (2) and can be comfortably reached by both the left and right hands of a user of the device (1). The housing (2) has two oppositely located wall openings (6, 7) and a hand support surface (8, 9) with a thumb support (12, 13) assigned to each wall opening (6, 7) in the lightray treatment chamber (3). At least two light sources (10, 11) are arranged in the lightray treatment chamber (3), of which the first light source (10) is used for treating the thumb with light and is arranged in front of the thumb supports (12, 13) of the hand support surfaces (8, 9), and the second light source (11) is arranged in the ceiling of the lightray treatment chamber (3).