An endoscope apparatus comprising: an endoscope including an insert section to be inserted into a body cavity; an illumination window for directing light therethrough and an observation window for observing an illuminated internal portion of the body cavity, arranged at a distal end portion of the insert section; a light source configured to selectively output visible light and narrow-band light through the illumination window; wherein the light source includes: a light source unit configured to generate visible observation light, a rotating filter arranged in front of the light source unit and configured to be rotated by a motor, said rotating filter having a dual structure which includes two sets of filters (28, 29), one on an inner ring portion and the other on an outer ring portion, the first filter set on the inner ring portion including three filters (R1, G1, B1) for standard observation, and the second filter set on the outer ring portion including three filters (R2, G2, B3) for narrow-band imaging; a blood flow changing section configured to provide one of a temperature change and vibration energy of an electromagnetic wave to a vessel in a near-surface region of a living organ inside the body cavity, so as to change a blood flow of blood flowing through said vessel; the endoscopic apparatus characterized in that: the blood flow changing section is further configured to be operatively driven to provide the one of a temperature change and vibration energy of an electromagnetic wave so as to increase a blood flow of blood flowing through said vessel when an operation mode is switched from the standard observation mode to the narrow-band imaging observation mode. an endoscope including an insert section to be inserted into a body cavity; an illumination window for directing light therethrough and an observation window for observing an illuminated internal portion of the body cavity, arranged at a distal end portion of the insert section; a light source configured to selectively output visible light and narrow-band light through the illumination window; wherein the light source includes: a light source unit configured to generate visible observation light, a rotating filter arranged in front of the light source unit and configured to be rotated by a motor, said rotating filter having a dual structure which includes two sets of filters (28, 29), one on an inner ring portion and the other on an outer ring portion, the first filter set on the inner ring portion including three filters (R1, G1, B1) for standard observation, and the second filter set on the outer ring portion including three filters (R2, G2, B3) for narrow-band imaging; a blood flow changing section configured to provide one of a temperature change and vibration energy of an electromagnetic wave to a vessel in a near-surface region of a living organ inside the body cavity, so as to change a blood flow of blood flowing through said vessel; a light source unit configured to generate visible observation light, a rotating filter arranged in front of the light source unit and configured to be rotated by a motor, said rotating filter having a dual structure which includes two sets of filters (28, 29), one on an inner ring portion and the other on an outer ring portion, the first filter set on the inner ring portion including three filters (R1, G1, B1) for standard observation, and the second filter set on the outer ring portion including three filters (R2, G2, B3) for narrow-band imaging; a blood flow changing section configured to provide one of a temperature change and vibration energy of an electromagnetic wave to a vessel in a near-surface region of a living organ inside the body cavity, so as to change a blood flow of blood flowing through said vessel; the endoscopic apparatus characterized in that: the blood flow changing section is further configured to be operatively driven to provide the one of a temperature change and vibration energy of an electromagnetic wave so as to increase a blood flow of blood flowing through said vessel when an operation mode is switched from the standard observation mode to the narrow-band imaging observation mode. the blood flow changing section is further configured to be operatively driven to provide the one of a temperature change and vibration energy of an electromagnetic wave so as to increase a blood flow of blood flowing through said vessel when an operation mode is switched from the standard observation mode to the narrow-band imaging observation mode.