A case for an endless transmission member (C1, C2), the case comprising: a first case member configured to be attached to a vehicle-mounted internal combustion engine ; and a second case member attached to the first case member , wherein the first case member and the second case member define an accommodation chamber (R) configured to accommodate an endless transmission member (C1, C2) looped over a plurality of rotating bodies of the vehicle-mounted internal combustion engine , wherein the first case member includes a main wall portion , which extends along a vertical direction in an orientation of the case when the vehicle-mounted internal combustion engine is installed in a vehicle, the main wall portion is arranged between the accommodation chamber (R) and an inside of the vehicle-mounted internal combustion engine and includes a communication hole extending through the main wall portion along a thickness of the main wall portion to connect the accommodation chamber (R) to the inside of the vehicle-mounted internal combustion engine , the first case member or the second case member includes a guide rib configured to guide lubricant from the accommodation chamber (R) to the inside of the vehicle-mounted internal combustion engine through the communication hole , the guide rib extending from an opening edge of the communication hole toward the inside of the accommodation chamber (R), and in the orientation of the case when the vehicle-mounted internal combustion engine is installed in the vehicle, the guide rib is provided along a lower part of the opening edge of the communication hole including a lowest end of the opening edge and includes an upper surface arranged to receive the lubricant in the accommodation chamber (R) and lead the lubricant toward the opening edge . a first case member configured to be attached to a vehicle-mounted internal combustion engine ; and a second case member attached to the first case member , wherein the first case member and the second case member define an accommodation chamber (R) configured to accommodate an endless transmission member (C1, C2) looped over a plurality of rotating bodies of the vehicle-mounted internal combustion engine , wherein the first case member includes a main wall portion , which extends along a vertical direction in an orientation of the case when the vehicle-mounted internal combustion engine is installed in a vehicle, the main wall portion is arranged between the accommodation chamber (R) and an inside of the vehicle-mounted internal combustion engine and includes a communication hole extending through the main wall portion along a thickness of the main wall portion to connect the accommodation chamber (R) to the inside of the vehicle-mounted internal combustion engine , the first case member or the second case member includes a guide rib configured to guide lubricant from the accommodation chamber (R) to the inside of the vehicle-mounted internal combustion engine through the communication hole , the guide rib extending from an opening edge of the communication hole toward the inside of the accommodation chamber (R), and in the orientation of the case when the vehicle-mounted internal combustion engine is installed in the vehicle, the guide rib is provided along a lower part of the opening edge of the communication hole including a lowest end of the opening edge and includes an upper surface arranged to receive the lubricant in the accommodation chamber (R) and lead the lubricant toward the opening edge . <EOS>