It is an object of the present invention to drastically reduce the likelihood of failure in sampling biological tissue. The solution means is a biopsy needle device (1) constructed in a manner such that an internal needle (2) is triggered in response to unlocking operation of internal needle locking means (8), after which a piston (14) is retracted by a piston retraction spring (15) in response to unlocking operation of piston locking means (16), whereby negative pressure is generated in a recess (2a) of the internal needle (2) resulting in suction of biological tissue into the recess (2a), and an external needle (3) is triggered in response to unlocking operation of external needle locking means (9), thereby cutting and sampling the biological tissue which has been drawn into the recess (2a).