To provide a small-sized prayer box in which a religious tablet is housed which can be carried by putting it into a bag or a pocket and easily assembled into a shape of an altar like a Buddhist alter or the like by using the box and the religious tablet in case of necessity.

The portable prayer box comprises a religious tablet 10 on which, an object of religious belief like the name or the image of God or Buddha is expressed, a box main body 20 for housing the religious tablet 10, and a cover 30 covering the box main body 20. The religious tablet 10 is formed into plate-shape, and a holding tool 25 is formed to the inside of the box main body 20. The religious tablet 10 is held in a state of standing-up by inserting the lower end of the religious tablet 10 into a gap formed between a side plate 24 of the box main body 20 and the holding tool 25.