A sample processing apparatus includes: a sample processing unit comprising a moving mechanism and configured to perform a sample processing operation by moving the moving mechanism; a cover configured to cover the moving mechanism of the sample processing unit; a lock mechanism configured to lock the cover to prevent the cover from being opened; and a controller configured to control the lock mechanism, wherein the controller is configured to set either of a first mode and a second mode, wherein in the first mode, the cover is kept locked after the sample processing unit has completed the sample processing operation until an instruction to unlock the cover is received from a user, and in the second mode, the cover is automatically unlocked after the sample processing unit has completed the sample processing operation.