A living body tissue harvesting apparatus comprising: a hollow grip section, a tubular insertion section connected to the grip section and configured to be inserted into a body cavity; a gas supplying path for supplying a predetermined gas from an external gas supplying device into an inner space of the insertion section; a first opening part provided on the insertion section, communicating the inner space of the insertion section with the exterior of the apparatus, characterized in that the living body tissue harvesting device further comprises: a communication path comprising: a first passage communicating the inner space of the tubular insertion section with an inner space of the grip section, the inner space of the grip section, and a second passage, communicating the inner space of the grip section with the exterior of the apparatus, wherein, when inserted into a body cavity, the living body tissue harvesting apparatus is configured to supply the predetermined gas via the gas supplying path into the insertion section, from where the gas can be discharged to some extent through the first opening part into the body cavity and to some other extent via the communication path to the exterior of the apparatus outside the body cavity, until the pressure in the body cavity is increased to a predetermined level, where no gas can be discharged any more from the insertion section into the body cavity, but all of the predetermined gas supplied via the gas supplying path can be discharged via the communication path to the exterior of the apparatus outside the body cavity, so that an excessive pressure in the body cavity can be prevented. a hollow grip section, a tubular insertion section connected to the grip section and configured to be inserted into a body cavity; a gas supplying path for supplying a predetermined gas from an external gas supplying device into an inner space of the insertion section; a first opening part provided on the insertion section, communicating the inner space of the insertion section with the exterior of the apparatus, characterized in that the living body tissue harvesting device further comprises: a communication path comprising: a first passage communicating the inner space of the tubular insertion section with an inner space of the grip section, the inner space of the grip section, and a second passage, communicating the inner space of the grip section with the exterior of the apparatus, wherein, when inserted into a body cavity, the living body tissue harvesting apparatus is configured to supply the predetermined gas via the gas supplying path into the insertion section, from where the gas can be discharged to some extent through the first opening part into the body cavity and to some other extent via the communication path to the exterior of the apparatus outside the body cavity, until the pressure in the body cavity is increased to a predetermined level, where no gas can be discharged any more from the insertion section into the body cavity, but all of the predetermined gas supplied via the gas supplying path can be discharged via the communication path to the exterior of the apparatus outside the body cavity, so that an excessive pressure in the body cavity can be prevented. a communication path comprising: a first passage communicating the inner space of the tubular insertion section with an inner space of the grip section, the inner space of the grip section, and a second passage, communicating the inner space of the grip section with the exterior of the apparatus, wherein, when inserted into a body cavity, the living body tissue harvesting apparatus is configured to supply the predetermined gas via the gas supplying path into the insertion section, from where the gas can be discharged to some extent through the first opening part into the body cavity and to some other extent via the communication path to the exterior of the apparatus outside the body cavity, until the pressure in the body cavity is increased to a predetermined level, where no gas can be discharged any more from the insertion section into the body cavity, but all of the predetermined gas supplied via the gas supplying path can be discharged via the communication path to the exterior of the apparatus outside the body cavity, so that an excessive pressure in the body cavity can be prevented. a first passage communicating the inner space of the tubular insertion section with an inner space of the grip section, the inner space of the grip section, and a second passage, communicating the inner space of the grip section with the exterior of the apparatus, wherein, when inserted into a body cavity, the living body tissue harvesting apparatus is configured to supply the predetermined gas via the gas supplying path into the insertion section, from where the gas can be discharged to some extent through the first opening part into the body cavity and to some other extent via the communication path to the exterior of the apparatus outside the body cavity, until the pressure in the body cavity is increased to a predetermined level, where no gas can be discharged any more from the insertion section into the body cavity, but all of the predetermined gas supplied via the gas supplying path can be discharged via the communication path to the exterior of the apparatus outside the body cavity, so that an excessive pressure in the body cavity can be prevented.