An imaging apparatus in which there is connected an optical probe unit including a transmitting and receiving unit which carries out transmission and reception of light continuously, reflected light from a body cavity is obtained at the transmitting and receiving unit while making rotational movement of the transmitting and receiving unit and longitudinal movement inside the body cavity, a cross-sectional image in the longitudinal direction of the body cavity is generated based on interference signal, representing positional information and intensity, generated by the obtained reflected light, comprising: an obtaining unit (214, 323) for obtaining signals which are generated every time when the transmitting and receiving unit carries out transmission and reception of light and which indicate positional information and intensity distribution of the interference signal from the transmitting and receiving position of the light to a certain depth position inside the body cavity, and a judgment unit (233, 338) for judging whether or not the optical probe unit is in a normal state based on: - determining existence or non-existence of intensity change in at least a portion of signals obtained by the obtaining unit (214, 323), - determining existence or non-existence of change of position in the depth direction in which the portion of signals appear, or - determining change quantity per unit time with respect to the position in which the portion of signals appear, characterized in that the judgment unit (233, 338) is adapted to carry out judgment by using at least one of the following signals -, representing positional information and intensity; as the portion of the signal: a signal (901, 911) corresponding to reflected light from a surface position of a lens constituting at least a part of the transmitting and receiving unit, a signal (902, 912) corresponding to light reflected from an inner surface position of the catheter sheath, (c) a signal (903, 913) corresponding to light reflected from an outer surface position of the catheter sheath. an obtaining unit (214, 323) for obtaining signals which are generated every time when the transmitting and receiving unit carries out transmission and reception of light and which indicate positional information and intensity distribution of the interference signal from the transmitting and receiving position of the light to a certain depth position inside the body cavity, and a judgment unit (233, 338) for judging whether or not the optical probe unit is in a normal state based on: - determining existence or non-existence of intensity change in at least a portion of signals obtained by the obtaining unit (214, 323), - determining existence or non-existence of change of position in the depth direction in which the portion of signals appear, or - determining change quantity per unit time with respect to the position in which the portion of signals appear, - determining existence or non-existence of intensity change in at least a portion of signals obtained by the obtaining unit (214, 323), - determining existence or non-existence of change of position in the depth direction in which the portion of signals appear, or - determining change quantity per unit time with respect to the position in which the portion of signals appear, characterized in that the judgment unit (233, 338) is adapted to carry out judgment by using at least one of the following signals -, representing positional information and intensity; as the portion of the signal: a signal (901, 911) corresponding to reflected light from a surface position of a lens constituting at least a part of the transmitting and receiving unit, a signal (902, 912) corresponding to light reflected from an inner surface position of the catheter sheath, (c) a signal (903, 913) corresponding to light reflected from an outer surface position of the catheter sheath. a signal (901, 911) corresponding to reflected light from a surface position of a lens constituting at least a part of the transmitting and receiving unit, a signal (902, 912) corresponding to light reflected from an inner surface position of the catheter sheath, (c) a signal (903, 913) corresponding to light reflected from an outer surface position of the catheter sheath.