To provide a connection structure of a water collecting device and a down pipe continuously visible when looked up from the lower side since a gap is absent between the water collecting device and a socket, prevented from being deteriorated in aesthetic appearance due to the accumulation of water and dirt, and having excellent-weatherability and durability.

In this connection structure, a down pipe 4 is connected to the water collecting device A through the socket 3. The water collecting device A comprises a water collecting device body 1 and a downward extending cylindrical body 2 vertically extending from a discharge hole 12 formed in the water collecting device 1 at the generally center of the bottom surface. The entire part of the bottom surface inner side 11 is formed in a tapered surface having a drainage slope toward the discharge hole 12. The bottom surface outer side 11a of the water collecting device body is formed in a flat surface. The downward extending cylindrical body 2 is fitted into the socket 3. The upper surface 31 of the socket 3 is installed on the flat surface of the bottom surface outer side 11a without a gap.