There is provided a fish egg processing apparatus capable of performing a predetermined processing on fertilized eggs with higher efficiency. A gene injection device 1 which is a fish egg processing apparatus according to the present invention includes a processing water tank 8 which processes collected fish eggs e and a processing device for injecting a predetermined substance into the fish eggs e positioned in the processing water tank 8, wherein the processing water tank 8 includes: a region prior to processing 81 where the width dimension is set such that a plurality of the fish eggs e are not allowed to lie side by side and form a line in order to house the fish eggs e prior to processing； and a region after processing 82 for housing the fish eggs e on which a predetermined processing has been performed.
