A method for producing a catalyst for unsaturated carboxylic acid synthesis, wherein the catalyst comprises molybdenum (Mo), vanadium and copper (Cu), the method comprising: (i) a drying step of obtaining a dried product by drying and heat-treating a starting material mixed liquid in which supply source compounds of respective catalyst component elements are integrated; (ii) a forming step of forming a catalyst precursor by supporting powder to be supported on a carrier comprising a particle aggregate, the powder to be supported being either the dried product or obtained from the dried product; and (iii) a calcining step of calcining the catalyst precursor to form the catalyst, wherein one of the following conditions (a) and (b) is fulfilled: (a) a first mass loss rate of the powder to be supported at 300°C is less than 5 percent by mass, and a difference between a second mass loss rate of the powder to be supported at 370°C and the first mass loss rate of the powder to be supported at 300°C is not less than 1 percent by mass and not more than 6 percent by mass, wherein the first and second mass loss rates of the powder to be supported are calculated from the following formula based on masses of the powder to be supported before and after heating the powder to be supported to 300°C and 370°C in an air atmosphere until there is no change in mass: mass loss rate (mass %) = [(mass of the powder to be supported before heating (g) - mass of the powder to be supported after heating (g))/mass of the powder to be supported before heating (g)] × 100; and (b) the heat-treating is carried out at a heat treatment temperature of not less than 270°C and not more than 330°C for not less than 30 minutes and not more than 2 hours. the catalyst comprises molybdenum (Mo), vanadium and copper (Cu), the method comprising: (i) a drying step of obtaining a dried product by drying and heat-treating a starting material mixed liquid in which supply source compounds of respective catalyst component elements are integrated; (ii) a forming step of forming a catalyst precursor by supporting powder to be supported on a carrier comprising a particle aggregate, the powder to be supported being either the dried product or obtained from the dried product; and (iii) a calcining step of calcining the catalyst precursor to form the catalyst, (i) a drying step of obtaining a dried product by drying and heat-treating a starting material mixed liquid in which supply source compounds of respective catalyst component elements are integrated; (ii) a forming step of forming a catalyst precursor by supporting powder to be supported on a carrier comprising a particle aggregate, the powder to be supported being either the dried product or obtained from the dried product; and (iii) a calcining step of calcining the catalyst precursor to form the catalyst, wherein one of the following conditions (a) and (b) is fulfilled: (a) a first mass loss rate of the powder to be supported at 300°C is less than 5 percent by mass, and a difference between a second mass loss rate of the powder to be supported at 370°C and the first mass loss rate of the powder to be supported at 300°C is not less than 1 percent by mass and not more than 6 percent by mass, wherein the first and second mass loss rates of the powder to be supported are calculated from the following formula based on masses of the powder to be supported before and after heating the powder to be supported to 300°C and 370°C in an air atmosphere until there is no change in mass: mass loss rate (mass %) = [(mass of the powder to be supported before heating (g) - mass of the powder to be supported after heating (g))/mass of the powder to be supported before heating (g)] × 100; and (b) the heat-treating is carried out at a heat treatment temperature of not less than 270°C and not more than 330°C for not less than 30 minutes and not more than 2 hours. (a) a first mass loss rate of the powder to be supported at 300°C is less than 5 percent by mass, and a difference between a second mass loss rate of the powder to be supported at 370°C and the first mass loss rate of the powder to be supported at 300°C is not less than 1 percent by mass and not more than 6 percent by mass, wherein the first and second mass loss rates of the powder to be supported are calculated from the following formula based on masses of the powder to be supported before and after heating the powder to be supported to 300°C and 370°C in an air atmosphere until there is no change in mass: mass loss rate (mass %) = [(mass of the powder to be supported before heating (g) - mass of the powder to be supported after heating (g))/mass of the powder to be supported before heating (g)] × 100; and (b) the heat-treating is carried out at a heat treatment temperature of not less than 270°C and not more than 330°C for not less than 30 minutes and not more than 2 hours.