A pressure-controlling device (10) includes a pump (21), a connection pipe (30), a first valve (41), and a second valve (42). The pump (21) has an inlet port (211) and an outlet port (212). The connection pipe (30) has a first end in communication with the outlet port (212), and a second end in communication with the inlet port (211) and that has a first space (31) that contains the first end, a second space (32) that contains the second end, and a third space (33) that is located between the first space (31) and the second space (32). The first valve (41) switches between a state in which the first space (31) and an exterior space of the connection pipe (30) are in communication with each other and the first space (31) and the third space (33) are not in communication with each other, and a state in which the first space (31) and the exterior space of the connection pipe (30) are not in communication with each other and the first space (31) and the third space (33) are in communication with each other. The second valve (42) switches between a state in which the second space (32) and the third space (33) are in communication with each other, and a state in which the second space (32) and the third space (33) are not in communication with each other.
