The present invention provides a mutant alkaline cellulase having enhanced anti-redeposition ability. The present invention provides a mutant alkaline cellulase having an amino acid sequence in which at least amino acid residue selected from the amino acid residues at the positions corresponding to positions 58, 45, 52, 56, 60, 64, 66, 71, 103, 119, 122, 123, 124, 125, 127, 130, 140, 161, 164, 175, 176, 178, 179, 181, 193, 194, 195, 196, 197, 199, 202, 203, 217, 225, 227, 228, 251, 267, 272, 276, 277, 280, 282, 297, 310, 312, 318, 324, 345, 354, 356, 357, 360, 363, 368, 418, 419, 420, 421, 422, 453, 454, 455, 457, 458, 459, 494, 495, 496, 500, 501, 502, 503, 504, 550, 551, 552, 604, 605, 606, 607, 608, 640, 641, 642, 644, 645, 646, 683, 684, 685, 690, 691, 692, 693, 694, 739, 740, and 741 of the amino acid sequence of an alkaline cellulase set forth in SEQ ID NO: 2 or of the amino acid sequence of an alkaline cellulase having at least 70% identity with the amino acid sequence of SEQ ID NO: 2, is substituted with other amino acid residue.