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.