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 configured to accommodate an endless transmission member (C1, C2) looped over a plurality of rotating bodies (51, 52, 53) 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 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 to the inside of the vehicle-mounted internal combustion engine, the first case member or the second case member includes a guide rib (35, 36, 37, 38, 41, 42) configured to guide lubricant from the accommodation chamber to the inside of the vehicle-mounted internal combustion engine through the communication hole, the guide rib (35, 36, 37, 38, 41, 42) extending from an opening edge of the communication hole toward the inside of the accommodation chamber, and in the orientation of the case when the vehicle-mounted internal combustion engine is installed in the vehicle, the guide rib (35, 36, 37, 38, 41, 42) 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 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 configured to accommodate an endless transmission member (C1, C2) looped over a plurality of rotating bodies (51, 52, 53) 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 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 to the inside of the vehicle-mounted internal combustion engine, the first case member or the second case member includes a guide rib (35, 36, 37, 38, 41, 42) configured to guide lubricant from the accommodation chamber to the inside of the vehicle-mounted internal combustion engine through the communication hole, the guide rib (35, 36, 37, 38, 41, 42) extending from an opening edge of the communication hole toward the inside of the accommodation chamber, and in the orientation of the case when the vehicle-mounted internal combustion engine is installed in the vehicle, the guide rib (35, 36, 37, 38, 41, 42) 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 and lead the lubricant toward the opening edge.