A manufacturing method of an acoustic sensor including a semiconductor substrate with a back chamber, a vibration thin film arranged on an upper side of the semiconductor substrate, an anchor arranged on an upper surface of the semiconductor substrate, a beam portion being integrally extended from the vibration thin film and having a distal end supported by the anchor, and a back plate fixed to the upper surface of the semiconductor substrate to cover the vibration thin film and the beam portion with a space, an acoustic vibration detected by the vibration thin film being converted to change in electrostatic capacitance between a fixed electrode film arranged on the back plate and the vibration thin film, the manufacturing method comprising the steps of: forming a first sacrifice layer and a second sacrifice layer between a surface of the semiconductor substrate and a lower surface of the vibration thin film and the beam portion, covering an upper surface of the vibration thin film and the beam portion with the second sacrifice layer and arranging the vibration thin film and the beam portion in a sacrifice layer including the first sacrifice layer and the second sacrifice layer; forming the back plate on the second sacrifice layer; forming the back chamber in the semiconductor substrate; removing the first sacrifice layer by etching; and removing one part of the second sacrifice layer by etching after removing the first sacrifice layer by etching and forming the anchor between said lower surface of the distal end of the beam portion and the surface of the semiconductor substrate from the remaining second sacrifice layer, wherein the first sacrifice layer and the second sacrifice layer are formed between the surface of the semiconductor substrate and the lower surface of the vibration thin film and the beam portion to cover at least one of the lower surface of the beam portion or a region facing the beam portion in the semiconductor substrate with the second sacrifice layer and an anchor layer is formed between the distal end of the beam portion and the semiconductor substrate separate from the first sacrifice layer with the same material as the first sacrifice layer; and one part of the second sacrifice layer is removed by etching after removing the first sacrifice layer by etching and the anchor is formed between the lower surface of the distal end of the beam portion and the surface of the semiconductor substrate from the remaining second sacrifice layer and the anchor layer. forming a first sacrifice layer and a second sacrifice layer between a surface of the semiconductor substrate and a lower surface of the vibration thin film and the beam portion, covering an upper surface of the vibration thin film and the beam portion with the second sacrifice layer and arranging the vibration thin film and the beam portion in a sacrifice layer including the first sacrifice layer and the second sacrifice layer; forming the back plate on the second sacrifice layer; forming the back chamber in the semiconductor substrate; removing the first sacrifice layer by etching; and removing one part of the second sacrifice layer by etching after removing the first sacrifice layer by etching and forming the anchor between said lower surface of the distal end of the beam portion and the surface of the semiconductor substrate from the remaining second sacrifice layer, wherein the first sacrifice layer and the second sacrifice layer are formed between the surface of the semiconductor substrate and the lower surface of the vibration thin film and the beam portion to cover at least one of the lower surface of the beam portion or a region facing the beam portion in the semiconductor substrate with the second sacrifice layer and an anchor layer is formed between the distal end of the beam portion and the semiconductor substrate separate from the first sacrifice layer with the same material as the first sacrifice layer; and one part of the second sacrifice layer is removed by etching after removing the first sacrifice layer by etching and the anchor is formed between the lower surface of the distal end of the beam portion and the surface of the semiconductor substrate from the remaining second sacrifice layer and the anchor layer.