A method for producing an ammoxidation catalyst, comprising: a step of preparing a precursor slurry that is a precursor of the catalyst; a drying step of obtaining a dry particle from the precursor slurry; and a calcination step of calcining the dry particle, wherein the step of preparing the precursor slurry is a step of mixing a first solution or slurry having a first pH and a second solution or slurry to obtain a solution or slurry having a second pH after completion of mixing, the time during which the pH of a mixture passes through a particular range having an upper limit and a lower limit while the second solution or slurry is mixed is 1-70 seconds, the upper limit and the lower limit being designated as a third pH and a fourth pH respectively, and the third pH and the fourth pH are set between the first pH and the second pH, characterized in that (i) the step of preparing the precursor slurry is a step of mixing the second solution or slurry comprising at least bismuth and iron with the first solution or slurry comprising at least molybdenum to obtain the precursor slurry, the pH of the first solution or slurry before the second solution or slurry is mixed is within a range of 5.5-7.0, the pH of the first solution or slurry after mixing of the second solution or slurry is completed is within a range of 0.1-1.9, and the pH of the mixture passes through a range of 4.0-2.0 while the second solution or slurry is mixed, or (ii) the step of preparing the precursor slurry is a step of mixing the second solution or slurry comprising at least molybdenum with the first solution or slurry comprising at least bismuth and iron to obtain a precursor slurry, the pH of the first solution or slurry before the second solution or slurry is mixed is within a range of 0.1-0.5, the pH of the first solution or slurry after mixing of the second solution or slurry is completed is within a range of 0.7-1.9, and the pH of the mixture passes through a range of 0.5-0.7 while the second solution or slurry is mixed. a step of preparing a precursor slurry that is a precursor of the catalyst; a drying step of obtaining a dry particle from the precursor slurry; and a calcination step of calcining the dry particle, wherein the step of preparing the precursor slurry is a step of mixing a first solution or slurry having a first pH and a second solution or slurry to obtain a solution or slurry having a second pH after completion of mixing, the time during which the pH of a mixture passes through a particular range having an upper limit and a lower limit while the second solution or slurry is mixed is 1-70 seconds, the upper limit and the lower limit being designated as a third pH and a fourth pH respectively, and the third pH and the fourth pH are set between the first pH and the second pH, characterized in that (i) the step of preparing the precursor slurry is a step of mixing the second solution or slurry comprising at least bismuth and iron with the first solution or slurry comprising at least molybdenum to obtain the precursor slurry, the pH of the first solution or slurry before the second solution or slurry is mixed is within a range of 5.5-7.0, the pH of the first solution or slurry after mixing of the second solution or slurry is completed is within a range of 0.1-1.9, and the pH of the mixture passes through a range of 4.0-2.0 while the second solution or slurry is mixed, or (ii) the step of preparing the precursor slurry is a step of mixing the second solution or slurry comprising at least molybdenum with the first solution or slurry comprising at least bismuth and iron to obtain a precursor slurry, the pH of the first solution or slurry before the second solution or slurry is mixed is within a range of 0.1-0.5, the pH of the first solution or slurry after mixing of the second solution or slurry is completed is within a range of 0.7-1.9, and the pH of the mixture passes through a range of 0.5-0.7 while the second solution or slurry is mixed. (i) the step of preparing the precursor slurry is a step of mixing the second solution or slurry comprising at least bismuth and iron with the first solution or slurry comprising at least molybdenum to obtain the precursor slurry, the pH of the first solution or slurry before the second solution or slurry is mixed is within a range of 5.5-7.0, the pH of the first solution or slurry after mixing of the second solution or slurry is completed is within a range of 0.1-1.9, and the pH of the mixture passes through a range of 4.0-2.0 while the second solution or slurry is mixed, or (ii) the step of preparing the precursor slurry is a step of mixing the second solution or slurry comprising at least molybdenum with the first solution or slurry comprising at least bismuth and iron to obtain a precursor slurry, the pH of the first solution or slurry before the second solution or slurry is mixed is within a range of 0.1-0.5, the pH of the first solution or slurry after mixing of the second solution or slurry is completed is within a range of 0.7-1.9, and the pH of the mixture passes through a range of 0.5-0.7 while the second solution or slurry is mixed.