A drive device for a construction machine, the drive device driving a driven portion in the construction machine, the drive device comprising: a motor serving as a drive source; and a speed reduction unit reducing speed of rotational force output from said motor, and transmitting the rotational force reduced in speed to said driven portion, wherein said motor has a motor shaft for outputting the rotational force, said speed reduction unit has a casing containing lubricant oil, a gear mechanism provided in the casing and reducing the speed of the rotational force output from said motor, a speed reduction output shaft for outputting the rotational force reduced in speed by the gear mechanism to said driven portion, and an oil receiver arranged above said gear mechanism in said casing, said oil receiver receiving the lubricant oil rising in said casing during operation of said drive device to store the lubricant oil, and said speed reduction unit and said motor are provided side by side such that a center of said speed reduction output shaft is aligned with a center of said motor shaft in a vertical direction, the gear mechanism being submerged in the lubricant oil contained in the inner space of the casing, said oil receiver forms a main storage space for storing the lubricant oil, and is arranged in said casing such that an oil passage for guiding said rising lubricant oil to the main storage space is formed between an outer surface of the oil receiver and an inner wall surface of said casing, and said oil receiver is provided with an oil drain opening, the oil drain opening designed to gradually discharge the lubricant oil stored in said main storage space toward said gear mechanism through the oil drain opening, characterized in that said speed reduction unit has a cylindrical body freely fitted on said motor shaft in a space above said gear mechanism in said casing, and a support member arranged above said oil receiver and mounted on said casing to support said cylindrical body, the cylindrical body having an inner diameter larger than an outer diameter of the motor shaft to allow the motor shaft to be inserted through the cylindrical body, and said oil receiver is mounted on an outer circumference portion of said cylindrical body. a motor serving as a drive source; and a speed reduction unit reducing speed of rotational force output from said motor, and transmitting the rotational force reduced in speed to said driven portion, wherein said motor has a motor shaft for outputting the rotational force, said speed reduction unit has a casing containing lubricant oil, a gear mechanism provided in the casing and reducing the speed of the rotational force output from said motor, a speed reduction output shaft for outputting the rotational force reduced in speed by the gear mechanism to said driven portion, and an oil receiver arranged above said gear mechanism in said casing, said oil receiver receiving the lubricant oil rising in said casing during operation of said drive device to store the lubricant oil, and said speed reduction unit and said motor are provided side by side such that a center of said speed reduction output shaft is aligned with a center of said motor shaft in a vertical direction, the gear mechanism being submerged in the lubricant oil contained in the inner space of the casing, said oil receiver forms a main storage space for storing the lubricant oil, and is arranged in said casing such that an oil passage for guiding said rising lubricant oil to the main storage space is formed between an outer surface of the oil receiver and an inner wall surface of said casing, and said oil receiver is provided with an oil drain opening, the oil drain opening designed to gradually discharge the lubricant oil stored in said main storage space toward said gear mechanism through the oil drain opening, characterized in that said speed reduction unit has a cylindrical body freely fitted on said motor shaft in a space above said gear mechanism in said casing, and a support member arranged above said oil receiver and mounted on said casing to support said cylindrical body, the cylindrical body having an inner diameter larger than an outer diameter of the motor shaft to allow the motor shaft to be inserted through the cylindrical body, and said oil receiver is mounted on an outer circumference portion of said cylindrical body.