A liquefied hydrogen loading arm configured to transport liquefied hydrogen, the loading arm comprising: a support frame structure including a base riser erected on a ground, an inboard boom having a lengthwise midway portion connected to an upper end portion of the base riser so as to be pivotal about a horizontal axis, an outboard boom pivotally connected to a distal end portion of the inboard boom, and a counterweight attached to a proximal end portion of the inboard boom; a flexible vacuum insulation double tube including a flexible metal inner tube, a flexible metal outer tube fitted on the inner tube, and a vacuum layer between the inner tube and the outer tube, the vacuum insulation double tube being disposed in an upward curved shape in a space below the support frame structure; a vacuum insulation double connecting tube connected to a distal end portion of the vacuum insulation double tube and connected to a distal end portion of the outboard boom; and a midway portion support mechanism configured to support a lengthwise midway portion of the vacuum insulation double tube on the support frame structure through a hard curved member curved upward in a convex shape; wherein the curved member is a steel band plate formed in a curved shape or a member obtained by forming a member having a groove-like section into a curved shape; and wherein the liquefied hydrogen loading arm further comprises an extended member provided for the outboard boom so as to extend downward from a distal end of the outboard boom, and a mount base erected on a ground on which the extended member is mounted when the liquefied hydrogen loading arm is in an inactive state. a support frame structure including a base riser erected on a ground, an inboard boom having a lengthwise midway portion connected to an upper end portion of the base riser so as to be pivotal about a horizontal axis, an outboard boom pivotally connected to a distal end portion of the inboard boom, and a counterweight attached to a proximal end portion of the inboard boom; a flexible vacuum insulation double tube including a flexible metal inner tube, a flexible metal outer tube fitted on the inner tube, and a vacuum layer between the inner tube and the outer tube, the vacuum insulation double tube being disposed in an upward curved shape in a space below the support frame structure; a vacuum insulation double connecting tube connected to a distal end portion of the vacuum insulation double tube and connected to a distal end portion of the outboard boom; and a midway portion support mechanism configured to support a lengthwise midway portion of the vacuum insulation double tube on the support frame structure through a hard curved member curved upward in a convex shape; wherein the curved member is a steel band plate formed in a curved shape or a member obtained by forming a member having a groove-like section into a curved shape; and wherein the liquefied hydrogen loading arm further comprises an extended member provided for the outboard boom so as to extend downward from a distal end of the outboard boom, and a mount base erected on a ground on which the extended member is mounted when the liquefied hydrogen loading arm is in an inactive state.