A method performed by a control device, comprising at least one computer and being configured to receive information about changing a drill bit, the method performed for changing a drill bit in a rock drilling unit, which drill bit is configured to be connected to at least one drill rod by a first threaded connection, the rock drilling unit comprising: a first feeding device for feeding the at least one drill rod and the drill bit in an axial direction; a rotating device, which is configured to generate a rotational movement of the at least one drill rod and the drill bit; an impact device for providing impact pulses on the at least one drill rod and the drill bit; and a drill bit changer for changing drill bits on the at least one drill rod, the method comprising: receiving information about changing the drill bit; controlling the impact device for punching the drill bit against a bottom of a formed drill bore for loosening the first threaded connection between the drill bit and the at least one drill rod; controlling the first feeding device for moving the at least one drill rod and the drill bit out of the drill bore; controlling gripping elements of a rod handling system for gripping the at least one drill rod, which is connected to the rotating device; controlling the rotating device for tightening a second threaded connection between the at least one drill rod and the rotating device, controlling the rotating device for removing the drill bit from the at least one drill rod; controlling the drill bit changer for changing and replacing the drill bit; and controlling the rotating device for attaching the at least one drill rod to the drill bit by the first threaded connection. a first feeding device for feeding the at least one drill rod and the drill bit in an axial direction; a rotating device, which is configured to generate a rotational movement of the at least one drill rod and the drill bit; an impact device for providing impact pulses on the at least one drill rod and the drill bit; and a drill bit changer for changing drill bits on the at least one drill rod, the method comprising: receiving information about changing the drill bit; controlling the impact device for punching the drill bit against a bottom of a formed drill bore for loosening the first threaded connection between the drill bit and the at least one drill rod; controlling the first feeding device for moving the at least one drill rod and the drill bit out of the drill bore; controlling gripping elements of a rod handling system for gripping the at least one drill rod, which is connected to the rotating device; controlling the rotating device for tightening a second threaded connection between the at least one drill rod and the rotating device, controlling the rotating device for removing the drill bit from the at least one drill rod; controlling the drill bit changer for changing and replacing the drill bit; and controlling the rotating device for attaching the at least one drill rod to the drill bit by the first threaded connection. receiving information about changing the drill bit; controlling the impact device for punching the drill bit against a bottom of a formed drill bore for loosening the first threaded connection between the drill bit and the at least one drill rod; controlling the first feeding device for moving the at least one drill rod and the drill bit out of the drill bore; controlling gripping elements of a rod handling system for gripping the at least one drill rod, which is connected to the rotating device; controlling the rotating device for tightening a second threaded connection between the at least one drill rod and the rotating device, controlling the rotating device for removing the drill bit from the at least one drill rod; controlling the drill bit changer for changing and replacing the drill bit; and controlling the rotating device for attaching the at least one drill rod to the drill bit by the first threaded connection.