A bicycle storage trunk to be attached to the frame of a closed frame bicycle. The storage trunk which includes a hinged door is pivotably mounted to the bicycle frame such that when the trunk is in a first position the door is precluded from opening and when the trunk is in a second position the door may be opened, thus enabling one to have access into the trunk. The device is designed to be locked to the bicycle frame in the first position in order to prevent the contents of the trunk from being stolen at such times that the bicycle may be left unattended. The trunk is constructed having a solid metal housing, so that the trunk may support and house relatively heavy objects. The interior of the trunk is covered by a soft layer of foam to prevent the contents therein from rattling or from being damaged by the metal housing.