A fume suction unit comprising: a suction fan; a casing covering the suction fan; and drive means for driving the suction fan; wherein the casing comprises a discharge-side end surface portion located on a discharge side of the suction fan and having a discharge port, a side surface portion connected with a peripheral edge of the discharge-side end surface portion and covering a periphery of the suction fan, a first suction section located on a suction side of the suction fan and having a passage communicated with an internal space of the side surface portion; characterized in that it comprises a second suction section provided to be communicated with the internal space of the side surface portion and having a suction characteristic different from that of the first suction section, and the fume suction unit comprises a first suction wall formed in a ring shape extending over an entire periphery of the side surface portion and protruding from the side surface portion toward a side opposite to the discharge-side end surface portion, the first suction wall having a flared shape which gradually expands toward the side opposite to the discharge-side end surface portion; and a pair of second suction walls (19, 19) each formed to extend across the side surface portion and the first suction wall, the first suction wall has a partition wall portion located between the pair of second suction walls (19, 19); the first suction section has a first passage which comprises a first suction port formed by peripheral end of the first suction wall formed to be located a the sake plane and a space surrounded by the first suction wall and the first passage provides communication between the surrounded space and the internal space of the side surface portion; and the second suction section has a second passage which comprises a space between the pair of second suction walls (19, 19) as a second suction port and provides communication between the second suction port and the internal space of the side surface portion via a communication hole formed in the partition wall portion, the fume suction unit is adapted to switch between a first usage mode to perform suction from a second suction port of the second suction section via communication hole under a condition that the peripheral end of the first suction wall is placed on a loading surface so that the casing is turned down to allow the first suction port of the first suction section to be oriented downwardly and no gap is formed between the loading surface and the peripheral end, and a second usage mode to perform suction from the first suction port under a condition that the casing is erected where the fume suction unit is placed on a loading surface in such a manner that ends (19a, 19a) of the second suction walls (19, 19) are located on the side of the loading surface. a suction fan; a casing covering the suction fan; and drive means for driving the suction fan; wherein the casing comprises a discharge-side end surface portion located on a discharge side of the suction fan and having a discharge port, a side surface portion connected with a peripheral edge of the discharge-side end surface portion and covering a periphery of the suction fan, a first suction section located on a suction side of the suction fan and having a passage communicated with an internal space of the side surface portion; characterized in that it comprises a second suction section provided to be communicated with the internal space of the side surface portion and having a suction characteristic different from that of the first suction section, and the fume suction unit comprises a first suction wall formed in a ring shape extending over an entire periphery of the side surface portion and protruding from the side surface portion toward a side opposite to the discharge-side end surface portion, the first suction wall having a flared shape which gradually expands toward the side opposite to the discharge-side end surface portion; and a pair of second suction walls (19, 19) each formed to extend across the side surface portion and the first suction wall, the first suction wall has a partition wall portion located between the pair of second suction walls (19, 19); the first suction section has a first passage which comprises a first suction port formed by peripheral end of the first suction wall formed to be located a the sake plane and a space surrounded by the first suction wall and the first passage provides communication between the surrounded space and the internal space of the side surface portion; and the second suction section has a second passage which comprises a space between the pair of second suction walls (19, 19) as a second suction port and provides communication between the second suction port and the internal space of the side surface portion via a communication hole formed in the partition wall portion, the fume suction unit is adapted to switch between a first usage mode to perform suction from a second suction port of the second suction section via communication hole under a condition that the peripheral end of the first suction wall is placed on a loading surface so that the casing is turned down to allow the first suction port of the first suction section to be oriented downwardly and no gap is formed between the loading surface and the peripheral end, and a second usage mode to perform suction from the first suction port under a condition that the casing is erected where the fume suction unit is placed on a loading surface in such a manner that ends (19a, 19a) of the second suction walls (19, 19) are located on the side of the loading surface.