A membrane catalyst layer assembly production method for producing a membrane catalyst layer assembly (100, 200) by discharging catalyst ink having a solvent and a solid component onto an electrolyte membrane, comprising: forming (S12-S16) a first catalyst ink layer having a first porosity on the electrolyte membrane; and forming (S12-S16) a second catalyst ink layer having a second porosity, which is different from the first porosity, on the first catalyst ink layer, characterized in that: the first catalyst ink layer is formed by controlling the porosity of a catalyst ink layer that is formed by the catalyst ink making impact with the electrolyte membrane by adjusting the amount of solvent in the catalyst ink in drop form prior to impact with the electrolyte membrane by adjusting (S124, S125) at least one of a frequency and a flow rate at a time of discharging the catalyst ink to change a droplet volume of the catalyst ink; the second catalyst ink layer is formed by adjusting the amount of solvent in the catalyst ink in drop form prior to impact with the first catalyst ink layer by adjusting (S124, S125) at least one of the frequency and the flow rate at the time of discharging the catalyst ink to change a droplet volume of the catalyst ink; and the solid content concentration of the catalyst ink is changed by adjusting the amount of solvent in the catalyst ink by drying the catalyst ink while airborne. forming (S12-S16) a first catalyst ink layer having a first porosity on the electrolyte membrane; and forming (S12-S16) a second catalyst ink layer having a second porosity, which is different from the first porosity, on the first catalyst ink layer, characterized in that: the first catalyst ink layer is formed by controlling the porosity of a catalyst ink layer that is formed by the catalyst ink making impact with the electrolyte membrane by adjusting the amount of solvent in the catalyst ink in drop form prior to impact with the electrolyte membrane by adjusting (S124, S125) at least one of a frequency and a flow rate at a time of discharging the catalyst ink to change a droplet volume of the catalyst ink; the second catalyst ink layer is formed by adjusting the amount of solvent in the catalyst ink in drop form prior to impact with the first catalyst ink layer by adjusting (S124, S125) at least one of the frequency and the flow rate at the time of discharging the catalyst ink to change a droplet volume of the catalyst ink; and the solid content concentration of the catalyst ink is changed by adjusting the amount of solvent in the catalyst ink by drying the catalyst ink while airborne. the first catalyst ink layer is formed by controlling the porosity of a catalyst ink layer that is formed by the catalyst ink making impact with the electrolyte membrane by adjusting the amount of solvent in the catalyst ink in drop form prior to impact with the electrolyte membrane by adjusting (S124, S125) at least one of a frequency and a flow rate at a time of discharging the catalyst ink to change a droplet volume of the catalyst ink; the second catalyst ink layer is formed by adjusting the amount of solvent in the catalyst ink in drop form prior to impact with the first catalyst ink layer by adjusting (S124, S125) at least one of the frequency and the flow rate at the time of discharging the catalyst ink to change a droplet volume of the catalyst ink; and the solid content concentration of the catalyst ink is changed by adjusting the amount of solvent in the catalyst ink by drying the catalyst ink while airborne.