A transportation refrigeration unit (100, 100A, 100B, 100C), comprising: a box configured to be provided on a front face of a transported container of a trailer and having openings at respective opposite sides of the transported container of the trailer in a width direction; a compressor disposed at an inside of the box to compress a refrigerant; a heat-exchanger disposed at the inside of the box to cool the refrigerant supplied from the compressor; a heat-exchange blowing part disposed at the inside of the box to send air to the heat-exchanger; a drive source (30, 30A, 30B) disposed at the inside of the box to drive the compressor; a drive blowing part (25, 35) configured to send air, which flows in from the opening of a first side in the width direction, to the drive source, and to discharge the air from the opening of a second side in the width direction; an upper and lower partition plate configured to partition the inside of the box into an upper space in which at least the heat-exchanger and the heat-exchange blowing part are disposed and a lower space which is divided from the upper space and in which the drive source (30, 30A, 30B) is disposed; characterized in that the lower space is partitioned into a central space, between a first space and a second space in the width direction, by a first and second partition plates (13, 14), the first partition plate configured to partition the lower space into a first space communicating with the opening of the first side and forming a first flow passage which is capable of flowing the air from the first space to a central space in which the drive source is disposed; the second partition plate configured to partition the lower space into a second space communicating with the opening of the second side and forming a second flow passage which is capable of flowing the air from the central space to the second space, a shield part disposed on a straight line connecting the opening of the second side and the second flow passage and formed to cover and block the second flow passage when viewed from the second side; an electric unit disposed in the first space to control driving of the compressor, wherein the electric unit is disposed on a straight line connecting the opening of the first side and the first flow passage and disposed to cover and block the first flow passage when viewed from the first side, and wherein the front wall of the box is curved and the electric unit has a trapezoidal inclined face disposed in contact with a front wall portion of the box, and wherein a flow path along which air flows from the opening of the first side to the first flow passage is curved and formed by the electric unit. a box configured to be provided on a front face of a transported container of a trailer and having openings at respective opposite sides of the transported container of the trailer in a width direction; a compressor disposed at an inside of the box to compress a refrigerant; a heat-exchanger disposed at the inside of the box to cool the refrigerant supplied from the compressor; a heat-exchange blowing part disposed at the inside of the box to send air to the heat-exchanger; a drive source (30, 30A, 30B) disposed at the inside of the box to drive the compressor; a drive blowing part (25, 35) configured to send air, which flows in from the opening of a first side in the width direction, to the drive source, and to discharge the air from the opening of a second side in the width direction; an upper and lower partition plate configured to partition the inside of the box into an upper space in which at least the heat-exchanger and the heat-exchange blowing part are disposed and a lower space which is divided from the upper space and in which the drive source (30, 30A, 30B) is disposed; characterized in that the lower space is partitioned into a central space, between a first space and a second space in the width direction, by a first and second partition plates (13, 14), the first partition plate configured to partition the lower space into a first space communicating with the opening of the first side and forming a first flow passage which is capable of flowing the air from the first space to a central space in which the drive source is disposed; the second partition plate configured to partition the lower space into a second space communicating with the opening of the second side and forming a second flow passage which is capable of flowing the air from the central space to the second space, a shield part disposed on a straight line connecting the opening of the second side and the second flow passage and formed to cover and block the second flow passage when viewed from the second side; an electric unit disposed in the first space to control driving of the compressor, wherein the electric unit is disposed on a straight line connecting the opening of the first side and the first flow passage and disposed to cover and block the first flow passage when viewed from the first side, and wherein the front wall of the box is curved and the electric unit has a trapezoidal inclined face disposed in contact with a front wall portion of the box, and wherein a flow path along which air flows from the opening of the first side to the first flow passage is curved and formed by the electric unit.