PURPOSE: To provide a bicycle carrier basket that has been foldable in compact so as not to make it in the way at a time when it is not used.

CONSTITUTION: This carrier basket is provided with a first hinge part 20 to hold a bottom part 2e foldably in making it almost surface adherence to a rear side part 2b, a second hinge part 14 to hold the rest side parts 2a, 2c and 2d foldably in making them almost surface adherence to this folded bottom parts 2e, and a lock lever 3 to hold the bottom part 2e and these side parts 2a, 2c and 2d releasbly from the folded state via both the first and second hinge parts 14, respectively.