Robert Harvey was operating the machine when Nicholas Hall was pinned against a wall by the excavator bucket, causing fatal injuries.
The court heard Harvey's company, Front Row Builders, was building a vehicle wash bay for Peter Lawless Road Planing at an industrial estate in Blantyre, South Lanarkshire, on 7 May 2016.
Harvey was using the digger to lower cement and blocks into the excavation pit for the three men working there, including Hall, to use in building a wall. He tipped the bucket to empty the mortar contents and shouted to Hall to "scrape the rest out with a shovel".
Hall was pinned against the wall by the excavator bucket and died of blunt force injuries to his chest and abdomen.
The Health and Safety Executive (HSE) investigation found Harvey failed to undertake a sufficient assessment of the risks to those who had been instructed to work with him and was not appropriately trained to use the excavator.
He pleaded guilty to breaching S 7(a) and S 33(1)(a) of the Health and Safety at Work Act and was jailed for ten months at Hamilton Sheriff Court.
"Those in control of work have a responsibility to devise safe methods of working and to provide the necessary information, instruction and training to their workers in the safe system of working," warned HSE inspector Helen Diamond after the sentencing.
"If a suitable safe system of work had been in place prior to the incident, the death of this worker could have been prevented."