Ed Rogers Landscape Construction and Maintenance Ltd of Jericho Street, Thorverton, pleaded guilty at Exeter Magistrates Court to the offence under Section 2(1) of the Health and Safety at Work etc Act 1974.
The firm has been fined £6,000, and ordered to pay costs of £1,017.
The company had employed the 16 year old for just three weeks when the incident happened. The apprentice was shown how to operate a log splitter by the company owner, Edward Rogers, and then left to work alone on site.
While the teenager was operating the log splitter unsupervised he held a log in place and started the machine. The hydraulic blade of the log splitter came down onto the log and severed his finger.
The incident was investigated by the Health and Safety Executive (HSE) which found that while the boy was working alone on site at the time of the incident, there was no first aid given. The teenager was later taken to hospital but his injuries were too severe to save his finger.
Speaking after the hearing, HSE Inspector Simon Jones, said: "Work experience for young people is incredibly valuable and is to be encouraged but companies taking on apprentices must take into account the young person’s inexperience. As a result they should be fully supervised when operating dangerous machinery.
"The boy being isolated made the situation worse when there was no one on site to help him after suffering this appalling, life changing injury."