An extreme ultraviolet light source apparatus (1, 1A, 1B, 1C), comprising: a disk-shaped cathode; a first rotational shaft made of a metal to which the cathode is connected; a disc-shaped anode disposed apart from the cathode; a second rotational shaft made of a metal to which the anode is connected; a first tin supplier (22a, 26a) configured to coat the cathode with liquid-phase tin; a second tin supplier (22b, 26b) configured to coat the anode with liquid-phase tin; an energy beam irradiation device configured to irradiate the tin on the cathode with an energy beam to vaporize the tin and generate gas-phase tin in a gap between the cathode and the anode; an electric power supply configured to supply electric power to the cathode and anode to cause a discharge between the cathode and anode for generating a plasma in the gap between the cathode and anode, the plasma emitting extreme ultraviolet light; a first support structure made of a metal supporting the cathode; and a second support structure made of a metal supporting the anode, the first support structure and the second support structure being not in contact with each other, the first support structure having a first support wall portion and a first tubular portion protruding from the first support wall portion and surrounding the first rotational shaft, the first tubular portion being disposed between the first support wall portion and the cathode, the second support structure having a second support wall portion and a second tubular portion protruding from the second support wall portion and surrounding the second rotational shaft, the second tubular portion being disposed between the second support wall portion and the anode, the first support wall portion and the second support wall portion overlapping each other, the first support wall portion having a through-hole through which the second tubular portion is inserted, or the second support wall portion having a through-hole through which the first tubular portion is inserted. a disk-shaped cathode; a first rotational shaft made of a metal to which the cathode is connected; a disc-shaped anode disposed apart from the cathode; a second rotational shaft made of a metal to which the anode is connected; a first tin supplier (22a, 26a) configured to coat the cathode with liquid-phase tin; a second tin supplier (22b, 26b) configured to coat the anode with liquid-phase tin; an energy beam irradiation device configured to irradiate the tin on the cathode with an energy beam to vaporize the tin and generate gas-phase tin in a gap between the cathode and the anode; an electric power supply configured to supply electric power to the cathode and anode to cause a discharge between the cathode and anode for generating a plasma in the gap between the cathode and anode, the plasma emitting extreme ultraviolet light; a first support structure made of a metal supporting the cathode; and a second support structure made of a metal supporting the anode, the first support structure and the second support structure being not in contact with each other, the first support structure having a first support wall portion and a first tubular portion protruding from the first support wall portion and surrounding the first rotational shaft, the first tubular portion being disposed between the first support wall portion and the cathode, the second support structure having a second support wall portion and a second tubular portion protruding from the second support wall portion and surrounding the second rotational shaft, the second tubular portion being disposed between the second support wall portion and the anode, the first support wall portion and the second support wall portion overlapping each other, the first support wall portion having a through-hole through which the second tubular portion is inserted, or the second support wall portion having a through-hole through which the first tubular portion is inserted.