A hybrid type working machine comprising: a first electric motor which is adapted to perform a power running operation driven by a supply of electric power and a regenerating operation generating electric power; a first electric circuit which is adapted to control the power running operation and the regenerating operation of the first electric motor; a charge accumulating circuit which is adapted to supply electric power to the first electric motor and to accumulate electric power regenerated by the first electric motor; a control device which is adapted to control the first electric circuit and the charge accumulating circuit; and a start key which is adapted to activate the control device, wherein the charge accumulating circuit includes: a DC bus line which is connected to the first electric circuit and in which a smoothing capacitor is connected between a ground line and a power line; a charge accumulating capacitor with an internal resistance (Rc); a converter which connects the DC bus line and the charge accumulating capacitor to each other, and which is adapted to perform a discharge operation of supplying electric energy from the charge accumulating capacitor to the DC bus line and a charge operation of supplying electric energy from the DC bus line to the charge accumulating capacitor; a charging resistor which is connected in series to the charge accumulating capacitor; and a first switch which is adapted to perform switching between an ON state and an OFF state, the ON state allowing current to flow between the charge accumulating capacitor and the DC bus line, and the OFF state not allowing current to flow between the charge accumulating capacitor and the DC bus line, and wherein the control device is adapted to switch the first switch from the OFF state to the ON state due to the start key being turned on, to measure a physical quantity involved with a discharge characteristic of the charge accumulating capacitor with a discharge current flowing from the charge accumulating capacitor to the smoothing capacitor through the charging resistor and the converter,, characterised in that the control device is further adapted to calculate at least one of the internal resistance (Rc) and a capacitance (Cc) of the charge accumulating capacitor on the basis of the measurement result. a first electric motor which is adapted to perform a power running operation driven by a supply of electric power and a regenerating operation generating electric power; a first electric circuit which is adapted to control the power running operation and the regenerating operation of the first electric motor; a charge accumulating circuit which is adapted to supply electric power to the first electric motor and to accumulate electric power regenerated by the first electric motor; a control device which is adapted to control the first electric circuit and the charge accumulating circuit; and a start key which is adapted to activate the control device, wherein the charge accumulating circuit includes: a DC bus line which is connected to the first electric circuit and in which a smoothing capacitor is connected between a ground line and a power line; a charge accumulating capacitor with an internal resistance (Rc); a converter which connects the DC bus line and the charge accumulating capacitor to each other, and which is adapted to perform a discharge operation of supplying electric energy from the charge accumulating capacitor to the DC bus line and a charge operation of supplying electric energy from the DC bus line to the charge accumulating capacitor; a charging resistor which is connected in series to the charge accumulating capacitor; and a first switch which is adapted to perform switching between an ON state and an OFF state, the ON state allowing current to flow between the charge accumulating capacitor and the DC bus line, and the OFF state not allowing current to flow between the charge accumulating capacitor and the DC bus line, and a DC bus line which is connected to the first electric circuit and in which a smoothing capacitor is connected between a ground line and a power line; a charge accumulating capacitor with an internal resistance (Rc); a converter which connects the DC bus line and the charge accumulating capacitor to each other, and which is adapted to perform a discharge operation of supplying electric energy from the charge accumulating capacitor to the DC bus line and a charge operation of supplying electric energy from the DC bus line to the charge accumulating capacitor; a charging resistor which is connected in series to the charge accumulating capacitor; and a first switch which is adapted to perform switching between an ON state and an OFF state, the ON state allowing current to flow between the charge accumulating capacitor and the DC bus line, and the OFF state not allowing current to flow between the charge accumulating capacitor and the DC bus line, and wherein the control device is adapted to switch the first switch from the OFF state to the ON state due to the start key being turned on, to measure a physical quantity involved with a discharge characteristic of the charge accumulating capacitor with a discharge current flowing from the charge accumulating capacitor to the smoothing capacitor through the charging resistor and the converter,, characterised in that the control device is further adapted to calculate at least one of the internal resistance (Rc) and a capacitance (Cc) of the charge accumulating capacitor on the basis of the measurement result.