A tire condition detecting apparatus, which is attached to a valve stem of a wheel assembly of a vehicle to be arranged in a tire of the wheel assembly, the apparatus comprising: a condition detecting section (42, 43) configured to detect a condition of the tire; a transmitting section configured to wirelessly transmit a signal containing information detected by the condition detecting section (42, 43); a receiving section capable of receiving the signal wirelessly transmitted from an external device; a control section configured to control the transmitting section and the receiving section; a property detecting section configured to detect an electrical property of the valve stem; and a battery, which is a power source for the tire condition detecting apparatus, wherein the control section is configured to operate in a control mode that is selected from a normal mode and a power saving mode, wherein, in the normal mode, the receiving section is maintained in a standby state, in which the receiving section is capable of receiving a wirelessly transmitted signal from the external device, and in the power saving mode, power consumption associated with reception of the wirelessly transmitted signal from the external device is less than that in the normal mode, the control section is configured to switch the control mode to the normal mode when an amount of change in the electrical property of the valve stem detected by the property detecting section exceeds a reference change amount, and the control section is configured to switch the control mode to the power saving mode when a termination condition is met in the normal mode, characterized in that the property detecting section is configured to detect a capacitance of the valve stem. a condition detecting section (42, 43) configured to detect a condition of the tire; a transmitting section configured to wirelessly transmit a signal containing information detected by the condition detecting section (42, 43); a receiving section capable of receiving the signal wirelessly transmitted from an external device; a control section configured to control the transmitting section and the receiving section; a property detecting section configured to detect an electrical property of the valve stem; and a battery, which is a power source for the tire condition detecting apparatus, wherein the control section is configured to operate in a control mode that is selected from a normal mode and a power saving mode, wherein, in the normal mode, the receiving section is maintained in a standby state, in which the receiving section is capable of receiving a wirelessly transmitted signal from the external device, and in the power saving mode, power consumption associated with reception of the wirelessly transmitted signal from the external device is less than that in the normal mode, the control section is configured to switch the control mode to the normal mode when an amount of change in the electrical property of the valve stem detected by the property detecting section exceeds a reference change amount, and the control section is configured to switch the control mode to the power saving mode when a termination condition is met in the normal mode,