A vehicular light-guiding body comprising: an incidence surface on which light from a light source is incident; a first reflection surface that internally reflects the light incident from the incidence surface and converts the light into substantially parallel light; a second reflection surface that internally reflects, forward in a front-rear direction, when the vehicular light guiding body is mounted on a vehicle, the substantially parallel light from the first reflection surface; a light blocking part that blocks a portion of the light reflected by the second reflection surface; a connecting surface that connects the second reflection surface and the light blocking part, and has a transmission surface which transmits a portion of the light reflected by the second reflection surface from a lower side in an up-down direction, when the vehicular light guiding body is mounted on a vehicle, to a guiding body outer part, and directs the light forward in the front-rear direction; a re-incidence surface that is disposed on a front side in the front-rear direction with respect to the transmission surface and on a lower side in the up-down direction with respect to the light blocking part, and allows the light transmitted from the transmission surface to the guiding body outer part to be re-incident; and an emission surface that emits the light internally reflected by the second reflection surface, and the light incident from the re-incidence surface; characterized in that the transmission surface includes transmission surfaces which are disposed on both sides of the vehicular light-guiding body with a space at a central part in a left-right direction when the vehicular light guiding body is mounted on a vehicle. an incidence surface on which light from a light source is incident; a first reflection surface that internally reflects the light incident from the incidence surface and converts the light into substantially parallel light; a second reflection surface that internally reflects, forward in a front-rear direction, when the vehicular light guiding body is mounted on a vehicle, the substantially parallel light from the first reflection surface; a light blocking part that blocks a portion of the light reflected by the second reflection surface; a connecting surface that connects the second reflection surface and the light blocking part, and has a transmission surface which transmits a portion of the light reflected by the second reflection surface from a lower side in an up-down direction, when the vehicular light guiding body is mounted on a vehicle, to a guiding body outer part, and directs the light forward in the front-rear direction; a re-incidence surface that is disposed on a front side in the front-rear direction with respect to the transmission surface and on a lower side in the up-down direction with respect to the light blocking part, and allows the light transmitted from the transmission surface to the guiding body outer part to be re-incident; and an emission surface that emits the light internally reflected by the second reflection surface, and the light incident from the re-incidence surface; characterized in that the transmission surface includes transmission surfaces which are disposed on both sides of the vehicular light-guiding body with a space at a central part in a left-right direction when the vehicular light guiding body is mounted on a vehicle.