To provide a culvert side ditch block which has a water collecting function, facilitates construction of a culvert side ditch having an arbitrarily adjustable water way gradient, and contributes to simplification of material control and efficient side ditch construction.

The culvert side ditch block 1 consists of a square cylindrical main body member 2 and a square cylindrical water collecting member 3. A lower opening edge 3b of the water collecting member 3 is connected to a square opening 2b formed in a central portion of a top plate 2a of the main body member 2, in a manner communicating with each other, and an upper opening edge 3a of the water collecting member 3 has a grating 4 mounted thereon. Then the opening edge 3b of the water collecting member 3 has bolts 5 arranged at four corners thereof in an axially protrudable/withdrawable manner, and peripheral surfaces of the water collecting member has work ports 6 formed therein at locations closer to the opening edge 3b. Further the top plate of the main body member 2 has tapered bottomed holes 7 formed therein at locations in the vicinity of the four corners of the opening 2b, into/from which the bolts 5 are insertable/removable.