PROBLEM TO BE SOLVED: To provide a group-III nitride semiconductor light-emitting element having a wide light emission spectrum width and a high light-emitting efficiency.SOLUTION: A group-III nitride semiconductor light-emitting element has a sapphire substrate 10. An n-contact layer 11, a hole block layer 12, a light-emitting layer 13, a p-clad layer 14, and a p-contact layer 15 are sequentially stacked on the sapphire substrate 10. The hole block layer 12 is made of n-AlGaN with a thickness of 100 Å. The light-emitting layer 13 has an MQW structure in which a pair of a well layer 130 made of InGaN and a barrier layer 131 made of GaN are laminated four times repeatedly. The well layers 130 are sequentially defined as well layers 130-1, 130-2, 130-3 and 130-4 from a side closer to the n-contact layer 11. When an In composition ratio in the well layers 130-i (1≤i≤4) is defined as xi (the unit is "%", hereinafter the same shall apply), the well layers 130-1 to 130-4 are configured to satisfy a relation of x1>x2>x3>x4.