A burner head of a burner for a gas cooktop, a burner, and a gas cooktop are provided. The burner head includes a plurality of supports, where each support includes a support surface for supporting a cooking utensil, the support is further provided with a plurality of gas ports from which gas flows out and forms a flame, and each support has a first working position and a second working position. When the supports are in the first working position, the burner head has a flat upper surface, and the support surfaces of the supports constitute the upper surface, and when the supports are in the second working position, the burner head has a concave surface, and the support surfaces of the supports constitute the concave surface. The shape of the burner head is changeable, so as to adapt to cooking utensils having different bottom outlines.