We propose an extension of n-ary Nambu-Poisson bracket to superspace R n|m and construct by means of superdeterminant a family of Nambu-Poisson algebras of even degree functions, where the parameter of this family is an invertible transformation of Grassmann coordinates in superspace R n|m . We prove in the case of the superspaces R n|1 and R n|2 that our n-ary bracket, defined with the help of superdeterminant, satisfies the conditions for n-ary Nambu-Poisson bracket, i.e. it is totally skew-symmetric and it satisfies the Leibniz rule and the Filippov-Jacobi identity (fundamental identity). We study the structure of n-ary bracket defined with the help of superdeterminant in the case of superspace R n|2 and show that it is the sum of usual n-ary Nambu-Poisson bracket and a new n-ary bracket, which we call χ-bracket, where χ is the product of two odd degree smooth functions.