Laser medium unit and laser device

A laser medium unit comprising:

• a plate-shaped laser gain medium which includes a first surface and a second surface opposite to the first surface and generates emission light by irradiation of excitation light from the first surface;
• a reflection member that is provided on the second surface so as to reflect the excitation light and the emission light;
• and
• a cooling member that cools the laser gain medium,
• wherein the laser gain medium includes an irradiation area which is irradiated with the excitation light and an outer area which is located outside the irradiation area when viewed from a thickness direction intersecting the first surface and the second surface,
• wherein the cooling member is thermally connected to the second surface through the reflection member so that a cooling area of the laser gain medium is formed on the second surface, and
• wherein an outer edge of the cooling area is located inside the irradiation area when viewed from the thickness direction.