To provide an emulsion fuel supply device capable of surely producing emulsion fuel and suppressing the increase in capacity with a simple structure.

An emulsion fuel supply device 5 makes emulsion fuel out of fuel, water and emulsifier supplied at a prescribed ratio of light oil:water = 7:3 or 8:2 and emulsifier of 1% or the like of the entire to be supplied to a diesel engine. The device includes a mixing pump 50 for force-feeding mixture of fuel, water and emulsifier, and with a mixer 53 for producing emulsion fuel by agitating force-fed mixture when the mixture passes through a mixer element 87 formed of a lump made by deformation and compression of metal fine wire.