A lower leg supporter that is made of a tubular knitted fabric knitted by rounding knitting and that is adapted to come in close contact with a wearer's body surface to assist the wearer's gastrocnemius muscle, comprising: a first anchor section that is knitted to surround an end of the tubular knitted fabric and that is adapted to secure the tubular knitted fabric to a knee part of the wearer's lower leg; a second anchor section that is knitted to surround the other end of the tubular knitted fabric and that is adapted to secure the tubular knitted fabric to an ankle part of the wearer's lower leg; and characterized by a gastrocnemius muscle support section that is knitted in a substantially X-shape intersected around a portion corresponding to a joining part of a gastrocnemius muscle and an Achilles tendon of the wearer on the back side of the tubular knitted fabric, that joins two ends of the substantially X-shaped knitted fabric to the first anchor section to be adapted to support the gastrocnemius muscle of the wearer, that joins the other two ends of the substantially X-shaped knitted fabric to the second anchor section, and that is adapted to extend to portions corresponding to both edges of the Achilles tendon of the wearer, wherein a base fabric section of the tubular knitted fabric is adapted to be arranged at least in a region which is surrounded with the first anchor section and the gastrocnemius muscle support section in a portion corresponding to the gastrocnemius muscle of the wearer and a region which is surrounded with the second anchor section and the gastrocnemius muscle support section in a portion corresponding to the Achilles tendon of the wearer, and wherein the gastrocnemius muscle support section is knitted so that the stretching resistance in the length direction of the tubular knitted fabric is larger than the stretching resistance of the base fabric section in the length direction of the tubular knitted fabric. a first anchor section that is knitted to surround an end of the tubular knitted fabric and that is adapted to secure the tubular knitted fabric to a knee part of the wearer's lower leg; a second anchor section that is knitted to surround the other end of the tubular knitted fabric and that is adapted to secure the tubular knitted fabric to an ankle part of the wearer's lower leg; and characterized by a gastrocnemius muscle support section that is knitted in a substantially X-shape intersected around a portion corresponding to a joining part of a gastrocnemius muscle and an Achilles tendon of the wearer on the back side of the tubular knitted fabric, that joins two ends of the substantially X-shaped knitted fabric to the first anchor section to be adapted to support the gastrocnemius muscle of the wearer, that joins the other two ends of the substantially X-shaped knitted fabric to the second anchor section, and that is adapted to extend to portions corresponding to both edges of the Achilles tendon of the wearer, wherein a base fabric section of the tubular knitted fabric is adapted to be arranged at least in a region which is surrounded with the first anchor section and the gastrocnemius muscle support section in a portion corresponding to the gastrocnemius muscle of the wearer and a region which is surrounded with the second anchor section and the gastrocnemius muscle support section in a portion corresponding to the Achilles tendon of the wearer, and wherein the gastrocnemius muscle support section is knitted so that the stretching resistance in the length direction of the tubular knitted fabric is larger than the stretching resistance of the base fabric section in the length direction of the tubular knitted fabric.