Provided is a state measuring device that measures the state of a cutting tool during cutting and machining. The cutting tool has one or more blade parts and is formed of a rotating body that causes the blade parts to contact, while rotating, an object to be machined and machines the object to be machined. The cutting tool is equipped with the following: a measuring unit that is attached on or near the blade parts and measures the state of the blade parts; an AD converter that is attached to the cutting tool, acquires measurement values measured by the measuring unit at a prescribed sampling rate, and performs AD conversion on the measurement values; a transmission unit that transmits, using digital wireless communication, the acquired measurement values each time the measurement values are acquired from the AD converter; and a monitor device that is disposed external to the cutting tool. The monitor device is provided with a receiving unit that receives the measurement values transmitted by the transmission unit, and a data management unit that, every time the measurement values are received by the receiving unit, causes a display unit to display the measurement values and also accumulates the measurement values in a memory unit.