A needleless syringe for injecting an injection objective substance into an injection target area by discharging the injection objective substance without using any injection needle, the needleless syringe comprising: an accommodating unit which is provided in a housing of the needleless syringe and which accommodates the injection objective substance; a driving unit (11, 12) which is operated when a voltage is applied to generate discharge energy in order to discharge the injection objective substance accommodated in the accommodating unit; a nozzle unit which includes a flow passage for allowing the injection objective substance applied with the discharge energy generated by the driving unit (11, 12) to flow therethrough and which discharges the injection objective substance from a discharge port formed at a forward end of the flow passage; a protruding member which is provided movably from a first position at which a forward end thereof protrudes from an end surface of the housing to a second position at which a protruding length of the forward end from the end surface of the housing is shorter than a protruding length provided at the first position and the forward end and the discharge port can be brought in contact with the injection target area; a maintaining mechanism which maintains the protruding member at the first position before the discharge energy is generated by the driving unit (11, 12); a power source circuit which applies a voltage to the driving unit (11, 12) when the protruding member having been maintained at the first position is moved to the second position by means of a pressing force received by the forward end of the protruding member; a syringe unit which collectively stores, as one unit, the accommodating unit, the driving unit (11, 12), and the nozzle unit in the housing, so that the discharge port of the nozzle unit is arranged at a forward end of the unit; and an annular elastic cover which is arranged on the end surface of the housing and which surrounds the forward end of the syringe unit, wherein the protruding member is formed as the syringe unit, and the first position is a position at which the forward end of the syringe unit protrudes from the end surface of the housing, and wherein the cover is formed so that a protruding length of the forward end of the cover from the end surface of the housing is not less than a protruding length of the forward end of the syringe unit from the end surface of the housing when the syringe unit is disposed at the first position, and the cover allows the syringe unit to move to the second position by being elastically deformed by the pressing force when the syringe unit is intruded by the pressing force. an accommodating unit which is provided in a housing of the needleless syringe and which accommodates the injection objective substance; a driving unit (11, 12) which is operated when a voltage is applied to generate discharge energy in order to discharge the injection objective substance accommodated in the accommodating unit; a nozzle unit which includes a flow passage for allowing the injection objective substance applied with the discharge energy generated by the driving unit (11, 12) to flow therethrough and which discharges the injection objective substance from a discharge port formed at a forward end of the flow passage; a protruding member which is provided movably from a first position at which a forward end thereof protrudes from an end surface of the housing to a second position at which a protruding length of the forward end from the end surface of the housing is shorter than a protruding length provided at the first position and the forward end and the discharge port can be brought in contact with the injection target area; a maintaining mechanism which maintains the protruding member at the first position before the discharge energy is generated by the driving unit (11, 12); a power source circuit which applies a voltage to the driving unit (11, 12) when the protruding member having been maintained at the first position is moved to the second position by means of a pressing force received by the forward end of the protruding member; a syringe unit which collectively stores, as one unit, the accommodating unit, the driving unit (11, 12), and the nozzle unit in the housing, so that the discharge port of the nozzle unit is arranged at a forward end of the unit; and an annular elastic cover which is arranged on the end surface of the housing and which surrounds the forward end of the syringe unit, wherein the protruding member is formed as the syringe unit, and the first position is a position at which the forward end of the syringe unit protrudes from the end surface of the housing, and wherein the cover is formed so that a protruding length of the forward end of the cover from the end surface of the housing is not less than a protruding length of the forward end of the syringe unit from the end surface of the housing when the syringe unit is disposed at the first position, and the cover allows the syringe unit to move to the second position by being elastically deformed by the pressing force when the syringe unit is intruded by the pressing force.