Method and machine for constructing a vertical shaft in soft rock by means of an excavator (4), comprising the steps of setting the working face of the shaft under water with a constant level so that the lower end of the excavator (4) is kept in the water, spraying concrete towards the shaft well exposed above the water level to form a lining thereon, mixing water and muck excavated from the working face to obtain a slurry and conveying the slurry out of the shaft.