An endoscope system comprising: an endoscope which has • an elongated insertion portion to be inserted into a subject and • a distal end portion comprising: ∘ a sensor of movement direction for detecting information about movement direction of the elongated insertion portion and ∘ an encoder for converting the information detected by the sensor of movement direction into an electric signal: • the endoscope being configured to acquire a front field-of-view image and a lateral field-of-view image of an object of observation in the subject; an inserting/extracting detection section configured to detect which one of an inserting direction and an extracting direction a moving direction of the insertion portion is, on the basis of the electric signal output by the encoder; an image processing section configured to generate an observation image comprising: • a front field-of-view image having a round shape and an outer circumference: • a lateral field-of-view image having a circular ring shape adjacent to the outer circumference of the front field-of-view image; wherein when the inserting/extracting detection section has detected an insertion direction the image processing section is configured to display a magnified image of the front field-of-view image and to change the display appearance of the lateral field-of-view image and when the inserting/extracting detection section has detected an extracting direction the image processing section is configured to display a magnified image of the lateral field-of-view image and to change the display appearance of the front Held-of-view image. an endoscope which has • an elongated insertion portion to be inserted into a subject and • a distal end portion comprising: ∘ a sensor of movement direction for detecting information about movement direction of the elongated insertion portion and ∘ an encoder for converting the information detected by the sensor of movement direction into an electric signal: • the endoscope being configured to acquire a front field-of-view image and a lateral field-of-view image of an object of observation in the subject; • an elongated insertion portion to be inserted into a subject and • a distal end portion comprising: ∘ a sensor of movement direction for detecting information about movement direction of the elongated insertion portion and ∘ an encoder for converting the information detected by the sensor of movement direction into an electric signal: ∘ a sensor of movement direction for detecting information about movement direction of the elongated insertion portion and ∘ an encoder for converting the information detected by the sensor of movement direction into an electric signal: • the endoscope being configured to acquire a front field-of-view image and a lateral field-of-view image of an object of observation in the subject; an inserting/extracting detection section configured to detect which one of an inserting direction and an extracting direction a moving direction of the insertion portion is, on the basis of the electric signal output by the encoder; an image processing section configured to generate an observation image comprising: • a front field-of-view image having a round shape and an outer circumference: • a lateral field-of-view image having a circular ring shape adjacent to the outer circumference of the front field-of-view image; • a front field-of-view image having a round shape and an outer circumference: • a lateral field-of-view image having a circular ring shape adjacent to the outer circumference of the front field-of-view image; wherein when the inserting/extracting detection section has detected an insertion direction the image processing section is configured to display a magnified image of the front field-of-view image and to change the display appearance of the lateral field-of-view image and when the inserting/extracting detection section has detected an extracting direction the image processing section is configured to display a magnified image of the lateral field-of-view image and to change the display appearance of the front Held-of-view image.