An ion source comprising: a cathode electrode arranged in one end of an inside of a chamber; a repeller electrode arranged in the other end of the inside of the chamber and facing a surface of the cathode electrode; a filament arranged on a back-surface side of the cathode electrode; a gas introduction hole to which a fluorine-compound gas is introduced, the gas introduction hole being provided in the chamber; and an emission hole through which a positively-charged ion is extracted out of the chamber, wherein a raw-material block is arranged in the chamber, the cathode electrode is heated by the filament through which a current is flowing, and a thermoelectron is emitted from an electron emitting surface of the surface of the cathode electrode toward the repeller electrode, the thermoelectron decomposing the fluorine-compound gas introduced through the gas introduction hole and generating plasma by reciprocally moving between the cathode electrode and the repeller electrode, and the positively-charged aluminum ion is generated by reaction of fluorine in the plasma with the raw-material block, the raw-material block is arranged near a side surface of the cathode electrode while being out of contact with the cathode electrode and the chamber, the raw-material block is aluminum nitride, and aluminum fluoride that is generated from the raw-material block and the fluorine-compound gas is decomposed by the thermoelectron so that an aluminum ion that is to be extracted out of the chamber is generated, characterized in that the fluorine-compound gas is a phosphorus-trifluoride gas, the raw-material block is arranged in a tip end of a raw-material supporting unit, a protruding portion that protrudes in an outward direction that is perpendicular to a side surface of the raw-material supporting unit is provided in the tip end of the raw-material supporting unit, the raw-material block is arranged on a surface of the protruding portion, the surface of the protruding portion facing the repeller electrode, and an attaching member is arranged on a back surface of the protruding portion, and the raw-material block is hung from the attaching member with screws, and the protruding portion is pinched between the raw-material block and the attaching member so that the raw-material block is fixed to the raw-material supporting unit. a cathode electrode arranged in one end of an inside of a chamber; a repeller electrode arranged in the other end of the inside of the chamber and facing a surface of the cathode electrode; a filament arranged on a back-surface side of the cathode electrode; a gas introduction hole to which a fluorine-compound gas is introduced, the gas introduction hole being provided in the chamber; and an emission hole through which a positively-charged ion is extracted out of the chamber, wherein a raw-material block is arranged in the chamber, the cathode electrode is heated by the filament through which a current is flowing, and a thermoelectron is emitted from an electron emitting surface of the surface of the cathode electrode toward the repeller electrode, the thermoelectron decomposing the fluorine-compound gas introduced through the gas introduction hole and generating plasma by reciprocally moving between the cathode electrode and the repeller electrode, and the positively-charged aluminum ion is generated by reaction of fluorine in the plasma with the raw-material block, the raw-material block is arranged near a side surface of the cathode electrode while being out of contact with the cathode electrode and the chamber, the raw-material block is aluminum nitride, and aluminum fluoride that is generated from the raw-material block and the fluorine-compound gas is decomposed by the thermoelectron so that an aluminum ion that is to be extracted out of the chamber is generated,