A method for obtaining a biological fertilizer with phosphorus from the apatite mineral solubilized by microorganisms, characterized in that it comprises the steps of: i) obtaining a homogenous mixture from aluminum-calcium phosphate rock powder to which a protein concentrate, posidonia, fresh manure, magnesium sulfate and ferrous sulfate are added as degradable mineral raw materials which are a source of nitrogen, energy and minerals for the phosphate-solubilizing organisms, as well as the phosphate-solubilizing organisms themselves as seed inoculant, in addition to the water necessary for achieving humidity of 25-35%, the temperature both during the mixing process and of the mixture itself being maintained below 42°C; ii) turning over the mixture obtained in i) for the purpose of maintaining the aerobic conditions, maintaining the minimum proportion of oxygen in the mixture at 5% to favor the development of the aerobic fermentation, as well as to cool the mixture, the periodicity of said turnovers depending on the temperature and oxygen conditions, maintained the temperature below 42°C; iii) maintaining the mixture under the conditions mentioned in i) and ii) for a period of 90-120 days, depending on the desired phosphorus solubilization percentage, of 20-25% of the phosphorus of the apatite mineral, protecting the mixture under a suitable cover and being carried out on a surface which allows maintaining the mentioned humidity and temperature conditions; iv) if necessary, adding the water necessary for maintaining a constant humidity of 25-35% to the mixture during composting steps i)-iii); v) at the end of the composting process, the temperature is allowed to increase to a temperature greater than 65°C for at least 1 hour to remove possible pathogenic germs suppressing the turnovers. vi) sieving the product obtained for its subsequent use forming part of another fertilizer, forming into pellets or direct use of the product. the homogenous mixture of i) including 10%-20% aluminum-calcium phosphate rock, 5%-10% protein concentrate, 10%-30% posidonia, 15%-25% fresh manure, 3%-5% magnesium sulfate, 3%-5% ferrous sulfate, as well as 10%-15% of phosphate-solubilizing organisms seed inoculant. i) obtaining a homogenous mixture from aluminum-calcium phosphate rock powder to which a protein concentrate, posidonia, fresh manure, magnesium sulfate and ferrous sulfate are added as degradable mineral raw materials which are a source of nitrogen, energy and minerals for the phosphate-solubilizing organisms, as well as the phosphate-solubilizing organisms themselves as seed inoculant, in addition to the water necessary for achieving humidity of 25-35%, the temperature both during the mixing process and of the mixture itself being maintained below 42°C; ii) turning over the mixture obtained in i) for the purpose of maintaining the aerobic conditions, maintaining the minimum proportion of oxygen in the mixture at 5% to favor the development of the aerobic fermentation, as well as to cool the mixture, the periodicity of said turnovers depending on the temperature and oxygen conditions, maintained the temperature below 42°C; iii) maintaining the mixture under the conditions mentioned in i) and ii) for a period of 90-120 days, depending on the desired phosphorus solubilization percentage, of 20-25% of the phosphorus of the apatite mineral, protecting the mixture under a suitable cover and being carried out on a surface which allows maintaining the mentioned humidity and temperature conditions; iv) if necessary, adding the water necessary for maintaining a constant humidity of 25-35% to the mixture during composting steps i)-iii); v) at the end of the composting process, the temperature is allowed to increase to a temperature greater than 65°C for at least 1 hour to remove possible pathogenic germs suppressing the turnovers. vi) sieving the product obtained for its subsequent use forming part of another fertilizer, forming into pellets or direct use of the product.