A high-arched foot orthosis adapted to be applied onto lower limbs of a human body, and comprising: two bodies, each one of the two bodies having a wearing space formed inside the body; a foot portion having a sole located on a bottom of the foot portion; an instep located on a top of the foot portion; an arch located on one of two vertical sides of the foot portion, facing the other one of the two bodies, and connected to the sole and the instep; and a lateral side located on the other one of the two vertical sides of the foot portion, and connected to the sole and the instep; an ankle portion connected to the foot portion; a shank portion connected to the ankle portion; a substrate surrounding the wearing space and extending from the foot portion to the shank portion through the ankle portion; and an elastomer disposed adjacent to the substrate and surrounding the wearing space, and when in use, extending from the instep of the foot portion at a cuneiform bone of a wearer through the arch and the sole in order, wrapping over a cuboid bone of the wearer, extending through the ankle portion inwardly and upwardly toward the shank portion, and wrapping over a talus bone of the wearer; and characterized in that each one of the two bodies has a knee portion connected to the shank portion; and a thigh portion connected to the knee portion; wherein the elastomer of each one of the two bodies extends to the thigh portion through a rear side of the shank portion, obliquely extends in combination with upward and outward turns through an outer side of the knee portion toward a front side of the thigh portion, and surrounds and fetters the thigh portion. two bodies, each one of the two bodies having a wearing space formed inside the body; a foot portion having a sole located on a bottom of the foot portion; an instep located on a top of the foot portion; an arch located on one of two vertical sides of the foot portion, facing the other one of the two bodies, and connected to the sole and the instep; and a lateral side located on the other one of the two vertical sides of the foot portion, and connected to the sole and the instep; an ankle portion connected to the foot portion; a shank portion connected to the ankle portion; a substrate surrounding the wearing space and extending from the foot portion to the shank portion through the ankle portion; and an elastomer disposed adjacent to the substrate and surrounding the wearing space, and when in use, extending from the instep of the foot portion at a cuneiform bone of a wearer through the arch and the sole in order, wrapping over a cuboid bone of the wearer, extending through the ankle portion inwardly and upwardly toward the shank portion, and wrapping over a talus bone of the wearer; and characterized in that each one of the two bodies has a knee portion connected to the shank portion; and a thigh portion connected to the knee portion; a knee portion connected to the shank portion; and a thigh portion connected to the knee portion; wherein the elastomer of each one of the two bodies extends to the thigh portion through a rear side of the shank portion, obliquely extends in combination with upward and outward turns through an outer side of the knee portion toward a front side of the thigh portion, and surrounds and fetters the thigh portion.