A measuring device configured to measure a state of a solution, comprising: a measuring unit configured to output a measurement signal associated with the state of the solution; a protection unit attached to the measuring unit; and a controller configured to obtain information on the state of the solution on the basis of the measurement signal output from the measuring unit, wherein the measuring unit has: a first part in a usable state that contributes to output of the measurement signal by coming into contact with the solution; and a second part that is isolated from the solution by the protection unit and is in a standby state for measurement, wherein: the information on the state of the solution includes a pH concentration; the measuring unit has a glass electrode unit, a first reference electrode unit and a second reference electrode unit used for glass electrode type pH measurement; the first part has a pair of the glass electrode unit and the first reference electrode unit; and the second part has the second reference electrode unit characterized in that: the protection unit has a protection plate configured to isolate the second part of the measuring unit from the solution; and the protection plate is composed of at least one of biodegradable resin and acid-soluble resin. a measuring unit configured to output a measurement signal associated with the state of the solution; a protection unit attached to the measuring unit; and a controller configured to obtain information on the state of the solution on the basis of the measurement signal output from the measuring unit, wherein the measuring unit has: a first part in a usable state that contributes to output of the measurement signal by coming into contact with the solution; and a second part that is isolated from the solution by the protection unit and is in a standby state for measurement, a first part in a usable state that contributes to output of the measurement signal by coming into contact with the solution; and a second part that is isolated from the solution by the protection unit and is in a standby state for measurement, wherein: the information on the state of the solution includes a pH concentration; the measuring unit has a glass electrode unit, a first reference electrode unit and a second reference electrode unit used for glass electrode type pH measurement; the first part has a pair of the glass electrode unit and the first reference electrode unit; and the second part has the second reference electrode unit characterized in that: the protection unit has a protection plate configured to isolate the second part of the measuring unit from the solution; and the protection plate is composed of at least one of biodegradable resin and acid-soluble resin. the information on the state of the solution includes a pH concentration; the measuring unit has a glass electrode unit, a first reference electrode unit and a second reference electrode unit used for glass electrode type pH measurement; the first part has a pair of the glass electrode unit and the first reference electrode unit; and the second part has the second reference electrode unit characterized in that: the protection unit has a protection plate configured to isolate the second part of the measuring unit from the solution; and the protection plate is composed of at least one of biodegradable resin and acid-soluble resin. the protection unit has a protection plate configured to isolate the second part of the measuring unit from the solution; and the protection plate is composed of at least one of biodegradable resin and acid-soluble resin.