A copper foil for a printed wiring board, said copper foil having a roughened layer, wherein on at least one surface of the copper foil, an average diameter at a particle root (D1) corresponding to a distance of 10% of a particle length is 0.2 μm to 1.0 μm, and a ratio of the particle length (L1) to the average diameter at the particle root (D1) is 15 or less when L1/D1, and a ratio of an average diameter at a particle middle (D2) corresponding to a distance of 50% of the particle length to the average diameter at the particle root (D1) is 1 to 4 when D2/D1.