A loop heat pipe comprising: an evaporator that is configured to vaporize working fluid; a condenser that is configured to liquefy the working fluid (Cv) vaporized by the evaporator; a liquid pipe that is configured to connect the condenser to the evaporator and includes a flow passage configured to send the working fluid liquefied by the condenser to the evaporator; and a vapor pipe that is configured to connect the evaporator to the condenser to send the working fluid (Cv) vaporized by the evaporator to the condenser, the loop heat pipe being characterized in that the liquid pipe is formed by a metal layer stack of a plurality of metal layers, the plurality of metal layers including a first metal layer (43,44) through which a first through hole (43X,44X) extends in a thickness-wise direction, the flow passage of the liquid pipe is formed by at least the first through hole (43X,44X) and has four walls that define the flow passage, and the liquid pipe further includes a plurality of porous bodies (14s,43s,44s,42t,45t) that are configured to form at least two of the four walls of the flow passage, wherein the plurality of porous bodies (14s,43s,44s,42t,45t) include a first porous body (43s,44s) formed in the first metal layer (43,44), and the first porous body (43s,44s) includes: a first bottomed hole (43u,44u) recessed in an upper surface of the first metal layer (43,44); a second bottomed hole (43d,44d) recessed in a lower surface of the first metal layer (43,44); and a fine pore (43z,44z) partially connecting the first bottomed hole (43u,44u) and the second bottomed hole (43d,44d). an evaporator that is configured to vaporize working fluid; a condenser that is configured to liquefy the working fluid (Cv) vaporized by the evaporator; a liquid pipe that is configured to connect the condenser to the evaporator and includes a flow passage configured to send the working fluid liquefied by the condenser to the evaporator; and a vapor pipe that is configured to connect the evaporator to the condenser to send the working fluid (Cv) vaporized by the evaporator to the condenser, the loop heat pipe being characterized in that the liquid pipe is formed by a metal layer stack of a plurality of metal layers, the plurality of metal layers including a first metal layer (43,44) through which a first through hole (43X,44X) extends in a thickness-wise direction, the flow passage of the liquid pipe is formed by at least the first through hole (43X,44X) and has four walls that define the flow passage, and the liquid pipe further includes a plurality of porous bodies (14s,43s,44s,42t,45t) that are configured to form at least two of the four walls of the flow passage, wherein the plurality of porous bodies (14s,43s,44s,42t,45t) include a first porous body (43s,44s) formed in the first metal layer (43,44), and the first porous body (43s,44s) includes: a first bottomed hole (43u,44u) recessed in an upper surface of the first metal layer (43,44); a second bottomed hole (43d,44d) recessed in a lower surface of the first metal layer (43,44); and a first bottomed hole (43u,44u) recessed in an upper surface of the first metal layer (43,44); a second bottomed hole (43d,44d) recessed in a lower surface of the first metal layer (43,44); and a fine pore (43z,44z) partially connecting the first bottomed hole (43u,44u) and the second bottomed hole (43d,44d).