A status monitoring system (40, 40A) to monitor a status of a rolling device, comprising: a contaminant water concentration monitoring device (6, 6A) configured to monitor a contaminant water concentration in a lubricant oil, the contaminant water concentration monitoring device (6, 6A) including: an electrostatic capacitance detector configured to detect an electrostatic capacitance in the lubricant oil; an oil temperature measuring instrument configured to detect an oil temperature in the lubricant oil; a lubricant oil reservoir formed as a portion of a housing configured to perform an oil bath lubrication; a measurement chamber disposed inside or outside of the housing; wherein the electrostatic capacitance detector and the oil temperature measuring instrument are provided within the measurement chamber, and a water concentration calculation section configured to calculate a contaminant water concentration in accordance with a predetermined rule from the electrostatic capacitance detected by the electrostatic capacitance detector and the oil temperature detected by the oil temperature measuring instrument, and characterized in that the contaminant water concentration monitoring device (6, 6A) further comprises: a stirrer positioned in said measurement chamber and configured to stir the lubricant oil within the measurement chamber. a contaminant water concentration monitoring device (6, 6A) configured to monitor a contaminant water concentration in a lubricant oil, the contaminant water concentration monitoring device (6, 6A) including: an electrostatic capacitance detector configured to detect an electrostatic capacitance in the lubricant oil; an oil temperature measuring instrument configured to detect an oil temperature in the lubricant oil; a lubricant oil reservoir formed as a portion of a housing configured to perform an oil bath lubrication; a measurement chamber disposed inside or outside of the housing; wherein the electrostatic capacitance detector and the oil temperature measuring instrument are provided within the measurement chamber, and a water concentration calculation section configured to calculate a contaminant water concentration in accordance with a predetermined rule from the electrostatic capacitance detected by the electrostatic capacitance detector and the oil temperature detected by the oil temperature measuring instrument, and an electrostatic capacitance detector configured to detect an electrostatic capacitance in the lubricant oil; an oil temperature measuring instrument configured to detect an oil temperature in the lubricant oil; a lubricant oil reservoir formed as a portion of a housing configured to perform an oil bath lubrication; a measurement chamber disposed inside or outside of the housing; wherein the electrostatic capacitance detector and the oil temperature measuring instrument are provided within the measurement chamber, and a water concentration calculation section configured to calculate a contaminant water concentration in accordance with a predetermined rule from the electrostatic capacitance detected by the electrostatic capacitance detector and the oil temperature detected by the oil temperature measuring instrument, and a stirrer positioned in said measurement chamber and configured to stir the lubricant oil within the measurement chamber.