A transparent display panel and a transparent display device are disclosed. The transparent display panel comprises a color filter substrate, an electrode layer, a blue phase liquid crystal layer configured to modulate an incident collimated natural light, and a light guide plate. The color filter substrate comprises a black matrix and pixel regions which are surrounded by the black matrix and arranged in a matrix, and each of the pixel regions on the color filter substrate is provided with a light shielding part at a central position, and an opening region surrounded by the light shielding part and the black matrix. The light guide plate is provided with a light exit region on a side close to the blue phase liquid crystal layer, the light exit region is arranged to correspond to the light shielding part in position, and in case the electrode layer does not apply a driving voltage to the blue phase liquid crystal layer, the collimated natural light which passes through the light exit region is incident on the light shielding part and is blocked by the light shielding part. The electrode layer is configured to apply the driving voltage to the blue phase liquid crystal layer to form a liquid crystal grating, and the blue phase liquid crystal receives different driving voltages at different positions in one of grating periods of the liquid crystal grating, so that the collimated natural light is diffracted by the liquid crystal grating and exits through the opening region.