To provide a joint construction method and a temporary gap holder for the method capable of maintaining a constant gap between box culverts at the time of the arrangement thereof in an abutted state, so as not to cause an adverse effect on a water stopping function due to the exposure of abutted flexible jointing materials to more than the required compression.

When a pair of box culverts 1 and 1 with flexible jointing materials 4 annually buried therein and partly exposed, are tightened and jointed to edges 2 axially abutted via a PC steel rod 13 led through the culverts 1 and 1 along an axial direction, a temporary gap holder 14 is provided between the edges 2 and 2, and then the culverts 1 and 1 are tightened, so that the flexible joining materials 4 and 4 come in contact with each other without a collapse and keep a gap (d) to maintain watertightness. Subsequently, the temporary gap holder 14 is removed.