A differential pressure detection device (1; 2; 3; 4; 5) configured to detect differential pressure that is a pressure difference between a high pressure side and a low pressure side, the differential pressure detection device (1; 2; 3; 4; 5) comprising: a case (10; 10A) having a substantially cylindrical shape and including a sliding cavity (12; 12A) open to a first end that is one end face; a spool (30; 30A; 30B; 30C; 30D) provided inside the sliding cavity (12; 12A), the spool (30; 30A; 30B; 30C; 30D) being movable along a center axis of the sliding cavity (12; 12A) inside the sliding cavity (12; 12A) and dividing the sliding cavity (12; 12A) into a space in the low pressure side and a space in the high pressure side; an elastic member (50; 50A; 50B; 50C; 50D) provided inside the sliding cavity (12; 12A); and a magnetic field detection element provided inside the case (10; 10A), wherein the spool (30; 30A; 30B; 30C; 30D) includes a first spool (31; 31A; 31B; 31C) provided with a magnet, the magnetic field detection element is provided opposite to the magnet with a bottom surface of the sliding cavity (12; 12A) interposed between the magnetic field detection element and the magnet, characterized by a second spool (32; 32A; 32B; 32C) having a diameter substantially identical to an inner diameter of the sliding cavity (12; 12A) and sliding inside the sliding cavity (12; 12A), wherein the first spool (31; 31A; 31B; 31C) is provided to face the space in the high pressure side, and the second spool (32; 32A; 32B; 32C) is provided to face the space in the low pressure side, the elastic member (50; 50A; 50B; 50C; 50D) includes a first elastic member (51; 51A; 51B; 51C) provided in the first spool (31; 31A; 31B; 31C) and configured to urge the first spool (31; 31A; 31B; 31C) toward the space in the high pressure side, and a second elastic member (52; 52A; 52B; 52C) provided in the second spool (32; 32A; 32B; 32C) and configured to urge the second spool (32; 32A; 32B; 32C) toward the space in the high pressure side, the first spool (31; 31A; 31B; 31C) is lighter than the second spool (32; 32A; 32B; 32C) in a state where the magnet is provided, urging force of the first elastic member (51; 51A; 51B; 51C) is smaller than urging force of the second elastic member (52; 52A; 52B; 52C), the first elastic member (51; 51A; 51B; 51C) and the second elastic member (52; 52A; 52B; 52C) are disposed in series, and one end of the first elastic member (51; 51A; 51B; 51C) is provided in the first spool (31; 31A; 31B; 31C), and the other end of the first elastic member (51; 51A; 51B; 51C) is provided in the second spool (32; 32A; 32B; 32C), wherein the first elastic member (51; 51A; 51B; 51C) is deformable between the first spool (31; 31A; 31B; 31C) and the second spool (32; 32A; 32B; 32C). a case (10; 10A) having a substantially cylindrical shape and including a sliding cavity (12; 12A) open to a first end that is one end face; a spool (30; 30A; 30B; 30C; 30D) provided inside the sliding cavity (12; 12A), the spool (30; 30A; 30B; 30C; 30D) being movable along a center axis of the sliding cavity (12; 12A) inside the sliding cavity (12; 12A) and dividing the sliding cavity (12; 12A) into a space in the low pressure side and a space in the high pressure side; an elastic member (50; 50A; 50B; 50C; 50D) provided inside the sliding cavity (12; 12A); and a magnetic field detection element provided inside the case (10; 10A), wherein the spool (30; 30A; 30B; 30C; 30D) includes a first spool (31; 31A; 31B; 31C) provided with a magnet, the magnetic field detection element is provided opposite to the magnet with a bottom surface of the sliding cavity (12; 12A) interposed between the magnetic field detection element and the magnet, characterized by a second spool (32; 32A; 32B; 32C) having a diameter substantially identical to an inner diameter of the sliding cavity (12; 12A) and sliding inside the sliding cavity (12; 12A), wherein the first spool (31; 31A; 31B; 31C) is provided to face the space in the high pressure side, and the second spool (32; 32A; 32B; 32C) is provided to face the space in the low pressure side, the elastic member (50; 50A; 50B; 50C; 50D) includes a first elastic member (51; 51A; 51B; 51C) provided in the first spool (31; 31A; 31B; 31C) and configured to urge the first spool (31; 31A; 31B; 31C) toward the space in the high pressure side, and a second elastic member (52; 52A; 52B; 52C) provided in the second spool (32; 32A; 32B; 32C) and configured to urge the second spool (32; 32A; 32B; 32C) toward the space in the high pressure side, the first spool (31; 31A; 31B; 31C) is lighter than the second spool (32; 32A; 32B; 32C) in a state where the magnet is provided, urging force of the first elastic member (51; 51A; 51B; 51C) is smaller than urging force of the second elastic member (52; 52A; 52B; 52C), the first elastic member (51; 51A; 51B; 51C) and the second elastic member (52; 52A; 52B; 52C) are disposed in series, and one end of the first elastic member (51; 51A; 51B; 51C) is provided in the first spool (31; 31A; 31B; 31C), and the other end of the first elastic member (51; 51A; 51B; 51C) is provided in the second spool (32; 32A; 32B; 32C), wherein the first elastic member (51; 51A; 51B; 51C) is deformable between the first spool (31; 31A; 31B; 31C) and the second spool (32; 32A; 32B; 32C).