Provided is a neutron capture therapy apparatus (lA) including: an accelerator (10) which emits a charged particle beam (P) atarget (T) which is irradiated with the charged particle beam (P)to generate a neutron beam (N) a beam transport path (48) that transports the charged particle beam(P), which is emitted from the accelerator (10), to the target (T) and a current detection portion (60) which detects a current value of the charged particle beam (P). The current detection portion (60) is provided inside the beam transport path (48) along an inner wall (48a) of the beam transport path (48) in a state of being insulated by the inner wall (48a).
