The invention discloses an alarm device for ore pulp leakage. The alarm device comprises a collecting pit (5) and a support (4). The support (4) is arranged on the collecting pit (5), and the support (4) is provided with a leakage position detection sensor (2) and a non-leakage position detection sensor (3). A floating ball (1) is arranged in the collecting pit (5), and the floating ball (1) is provided with a lower limit position detecting block (6) and an upper limit position detecting block (7). The alarm device for the ore pulp leakage is low in fault rate and capable of giving an alarm for ore pulp leakage in time.