The invention is a method and device for measuring the minimum miscibility pressure of two phases having application for enhanced oil recovery or CO2 geologic storage. In a pressure cell, gas is bubbled into a liquid, or conversely, liquid is dripped into a gas. The presence of bubbles or of drops is detected through the differential pressure variation measured between the inside of the cell and an injected phase injection line. This measurement is performed by means of a very accurate differential pressure sensor, for various pressures imposed within the cell. A relation between the number of bubbles or of drops formed per time unit and pressures within the cell is deduced therefrom. The minimum miscibility pressure of the two phases then corresponds to the pressure for which the inverse of the number of bubbles or of drops is zero, which is deduced by extrapolation of the relation.