A level indicator for measuring a water level, comprising: a water level indicator comprising a first diaphragm configured to measure pressure; a replaceable protective cover comprising a case surrounding the entire water level indicator from an outside thereof, the case comprising: a replaceable second diaphragm configured to transmit pressure from an outside of the protective cover to an inside of the protective cover ; a cylindrical body part that surrounds the water level indicator ; a first blocking part that blocks a first end of the cylindrical body part ; a flange disposed at a second end of the cylindrical body part ; and a second blocking part fixed to the flange and that blocks the second end, wherein the second diaphragm is interposed between the flange and the second blocking part , wherein the second blocking part comprises: an opening part disposed at a center of the second blocking part and by which the second diaphragm is exposed, the flange is separate from the second blocking part , and wherein the flange is fixed to the second blocking part with a plurality of fixing parts (50; 60) in a state where the second diaphragm is interposed between the flange and the second blocking part . a water level indicator comprising a first diaphragm configured to measure pressure; a replaceable protective cover comprising a case surrounding the entire water level indicator from an outside thereof, the case comprising: a replaceable second diaphragm configured to transmit pressure from an outside of the protective cover to an inside of the protective cover ; a cylindrical body part that surrounds the water level indicator ; a first blocking part that blocks a first end of the cylindrical body part ; a flange disposed at a second end of the cylindrical body part ; and a second blocking part fixed to the flange and that blocks the second end, wherein the second diaphragm is interposed between the flange and the second blocking part , wherein the second blocking part comprises: an opening part disposed at a center of the second blocking part and by which the second diaphragm is exposed, the flange is separate from the second blocking part , and wherein the flange is fixed to the second blocking part with a plurality of fixing parts (50; 60) in a state where the second diaphragm is interposed between the flange and the second blocking part . a replaceable second diaphragm configured to transmit pressure from an outside of the protective cover to an inside of the protective cover ; a cylindrical body part that surrounds the water level indicator ; a first blocking part that blocks a first end of the cylindrical body part ; a flange disposed at a second end of the cylindrical body part ; and a second blocking part fixed to the flange and that blocks the second end, wherein the second diaphragm is interposed between the flange and the second blocking part , wherein the second blocking part comprises: an opening part disposed at a center of the second blocking part and by which the second diaphragm is exposed, the flange is separate from the second blocking part , and wherein the flange is fixed to the second blocking part with a plurality of fixing parts (50; 60) in a state where the second diaphragm is interposed between the flange and the second blocking part . <EOS>